/*
- * Copyright (c) 2003, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */
 
 package java.lang;
 
-import sun.misc.FloatingDecimal;
+import jdk.internal.math.FloatingDecimal;
 import java.util.Arrays;
+import java.util.Spliterator;
+import java.util.stream.IntStream;
+import java.util.stream.StreamSupport;
+
+import static java.lang.String.COMPACT_STRINGS;
+import static java.lang.String.UTF16;
+import static java.lang.String.LATIN1;
+import static java.lang.String.checkIndex;
+import static java.lang.String.checkOffset;
 
 /**
  * A mutable sequence of characters.
  * <p>
  * Implements a modifiable string. At any point in time it contains some
  * particular sequence of characters, but the length and content of the
  * sequence can be changed through certain method calls.
  *
  * <p>Unless otherwise noted, passing a {@code null} argument to a constructor
  * or method in this class will cause a {@link NullPointerException} to be
  * thrown.
  *
  * @author      Michael McCloskey
  * @author      Martin Buchholz
  * @author      Ulf Zibis
  * @since       1.5
  */
 abstract class AbstractStringBuilder implements Appendable, CharSequence {
     /**
      * The value is used for character storage.
      */
-    char[] value;
+    byte[] value;
+
+    /**
+     * The id of the encoding used to encode the bytes in {@code value}.
+     */
+    byte coder;
 
     /**
      * The count is the number of characters used.
      */
     int count;
 
+    private static final byte[] EMPTYVALUE = new byte[0];
+
     /**
      * This no-arg constructor is necessary for serialization of subclasses.
      */
     AbstractStringBuilder() {
+        value = EMPTYVALUE;
     }
 
     /**
      * Creates an AbstractStringBuilder of the specified capacity.
      */
     AbstractStringBuilder(int capacity) {
-        value = new char[capacity];
+        if (COMPACT_STRINGS) {
+            value = new byte[capacity];
+            coder = LATIN1;
+        } else {
+            value = StringUTF16.newBytesFor(capacity);
+            coder = UTF16;
+        }
+    }
+
+    /**
+     * Compares the objects of two AbstractStringBuilder implementations lexicographically.
+     *
+     * @since 11
+     */
+    int compareTo(AbstractStringBuilder another) {
+        if (this == another) {
+            return 0;
+        }
+
+        byte val1[] = value;
+        byte val2[] = another.value;
+        int count1 = this.count;
+        int count2 = another.count;
+
+        if (coder == another.coder) {
+            return isLatin1() ? StringLatin1.compareTo(val1, val2, count1, count2)
+                              : StringUTF16.compareTo(val1, val2, count1, count2);
+        }
+        return isLatin1() ? StringLatin1.compareToUTF16(val1, val2, count1, count2)
+                          : StringUTF16.compareToLatin1(val1, val2, count1, count2);
     }
 
     /**
      * Returns the length (character count).
      *
      * @return  the length of the sequence of characters currently
      *          represented by this object
      */
     @Override
     public int length() {
         return count;
     }
 
     /**
      * Returns the current capacity. The capacity is the amount of storage
      * available for newly inserted characters, beyond which an allocation
      * will occur.
      *
      * @return  the current capacity
      */
     public int capacity() {
-        return value.length;
+        return value.length >> coder;
     }
 
     /**
      * Ensures that the capacity is at least equal to the specified minimum.
      * If the current capacity is less than the argument, then a new internal
      * array is allocated with greater capacity. The new capacity is the
      * larger of:
      * <ul>
      * <li>The {@code minimumCapacity} argument.
      * <li>Twice the old capacity, plus {@code 2}.
      * </ul>
      * If the {@code minimumCapacity} argument is nonpositive, this
      * method takes no action and simply returns.
      * Note that subsequent operations on this object can reduce the
      * actual capacity below that requested here.
      *
      * @param   minimumCapacity   the minimum desired capacity.
      */
     public void ensureCapacity(int minimumCapacity) {
-        if (minimumCapacity > 0)
+        if (minimumCapacity > 0) {
             ensureCapacityInternal(minimumCapacity);
+        }
     }
 
     /**
      * For positive values of {@code minimumCapacity}, this method
      * behaves like {@code ensureCapacity}, however it is never
      * synchronized.
      * If {@code minimumCapacity} is non positive due to numeric
      * overflow, this method throws {@code OutOfMemoryError}.
      */
     private void ensureCapacityInternal(int minimumCapacity) {
         // overflow-conscious code
-        if (minimumCapacity - value.length > 0) {
+        int oldCapacity = value.length >> coder;
+        if (minimumCapacity - oldCapacity > 0) {
             value = Arrays.copyOf(value,
-                    newCapacity(minimumCapacity));
+                    newCapacity(minimumCapacity) << coder);
         }
     }
 
     /**
      * The maximum size of array to allocate (unless necessary).
      * Some VMs reserve some header words in an array.
      * Attempts to allocate larger arrays may result in
      * OutOfMemoryError: Requested array size exceeds VM limit
      */
     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
 
     /**
      * Returns a capacity at least as large as the given minimum capacity.
      * Returns the current capacity increased by the same amount + 2 if
      * that suffices.
-     * Will not return a capacity greater than {@code MAX_ARRAY_SIZE}
-     * unless the given minimum capacity is greater than that.
+     * Will not return a capacity greater than
+     * {@code (MAX_ARRAY_SIZE >> coder)} unless the given minimum capacity
+     * is greater than that.
      *
      * @param  minCapacity the desired minimum capacity
      * @throws OutOfMemoryError if minCapacity is less than zero or
-     *         greater than Integer.MAX_VALUE
+     *         greater than (Integer.MAX_VALUE >> coder)
      */
     private int newCapacity(int minCapacity) {
         // overflow-conscious code
-        int newCapacity = (value.length << 1) + 2;
+        int oldCapacity = value.length >> coder;
+        int newCapacity = (oldCapacity << 1) + 2;
         if (newCapacity - minCapacity < 0) {
             newCapacity = minCapacity;
         }
-        return (newCapacity <= 0 || MAX_ARRAY_SIZE - newCapacity < 0)
+        int SAFE_BOUND = MAX_ARRAY_SIZE >> coder;
+        return (newCapacity <= 0 || SAFE_BOUND - newCapacity < 0)
             ? hugeCapacity(minCapacity)
             : newCapacity;
     }
 
     private int hugeCapacity(int minCapacity) {
-        if (Integer.MAX_VALUE - minCapacity < 0) { // overflow
+        int SAFE_BOUND = MAX_ARRAY_SIZE >> coder;
+        int UNSAFE_BOUND = Integer.MAX_VALUE >> coder;
+        if (UNSAFE_BOUND - minCapacity < 0) { // overflow
             throw new OutOfMemoryError();
         }
-        return (minCapacity > MAX_ARRAY_SIZE)
-            ? minCapacity : MAX_ARRAY_SIZE;
+        return (minCapacity > SAFE_BOUND)
+            ? minCapacity : SAFE_BOUND;
+    }
+
+    /**
+     * If the coder is "isLatin1", this inflates the internal 8-bit storage
+     * to 16-bit <hi=0, low> pair storage.
+     */
+    private void inflate() {
+        if (!isLatin1()) {
+            return;
+        }
+        byte[] buf = StringUTF16.newBytesFor(value.length);
+        StringLatin1.inflate(value, 0, buf, 0, count);
+        this.value = buf;
+        this.coder = UTF16;
     }
 
     /**
      * Attempts to reduce storage used for the character sequence.
      * If the buffer is larger than necessary to hold its current sequence of
      * characters, then it may be resized to become more space efficient.
      * Calling this method may, but is not required to, affect the value
      * returned by a subsequent call to the {@link #capacity()} method.
      */
     public void trimToSize() {
-        if (count < value.length) {
-            value = Arrays.copyOf(value, count);
+        int length = count << coder;
+        if (length < value.length) {
+            value = Arrays.copyOf(value, length);
         }
     }
 
     /**
      * Sets the length of the character sequence.
      * The sequence is changed to a new character sequence
      * whose length is specified by the argument. For every nonnegative
      * index <i>k</i> less than {@code newLength}, the character at
      * index <i>k</i> in the new character sequence is the same as the
      * character at index <i>k</i> in the old sequence if <i>k</i> is less
      * than the length of the old character sequence; otherwise, it is the
      * null character {@code '\u005Cu0000'}.
      *
      * In other words, if the {@code newLength} argument is less than
      * the current length, the length is changed to the specified length.
      * <p>
      * If the {@code newLength} argument is greater than or equal
      * to the current length, sufficient null characters
      * ({@code '\u005Cu0000'}) are appended so that
      * length becomes the {@code newLength} argument.
      * <p>
      * The {@code newLength} argument must be greater than or equal
      * to {@code 0}.
      *
      * @param      newLength   the new length
      * @throws     IndexOutOfBoundsException  if the
      *               {@code newLength} argument is negative.
      */
     public void setLength(int newLength) {
-        if (newLength < 0)
+        if (newLength < 0) {
             throw new StringIndexOutOfBoundsException(newLength);
-        ensureCapacityInternal(newLength);
-
-        if (count < newLength) {
-            Arrays.fill(value, count, newLength, '\0');
         }
-
+        ensureCapacityInternal(newLength);
+        if (count < newLength) {
+            if (isLatin1()) {
+                StringLatin1.fillNull(value, count, newLength);
+            } else {
+                StringUTF16.fillNull(value, count, newLength);
+            }
+        }
         count = newLength;
     }
 
     /**
      * Returns the {@code char} value in this sequence at the specified index.
      * The first {@code char} value is at index {@code 0}, the next at index
      * {@code 1}, and so on, as in array indexing.
      * <p>
      * The index argument must be greater than or equal to
      * {@code 0}, and less than the length of this sequence.
      *
      * <p>If the {@code char} value specified by the index is a
      * <a href="Character.html#unicode">surrogate</a>, the surrogate
      * value is returned.
      *
      * @param      index   the index of the desired {@code char} value.
      * @return     the {@code char} value at the specified index.
      * @throws     IndexOutOfBoundsException  if {@code index} is
      *             negative or greater than or equal to {@code length()}.
      */
     @Override
     public char charAt(int index) {
-        if ((index < 0) || (index >= count))
-            throw new StringIndexOutOfBoundsException(index);
-        return value[index];
+        checkIndex(index, count);
+        if (isLatin1()) {
+            return (char)(value[index] & 0xff);
+        }
+        return StringUTF16.charAt(value, index);
     }
 
     /**
      * Returns the character (Unicode code point) at the specified
      * index. The index refers to {@code char} values
      * (Unicode code units) and ranges from {@code 0} to
      * {@link #length()}{@code  - 1}.
      *
      * <p> If the {@code char} value specified at the given index
      * is in the high-surrogate range, the following index is less
      * than the length of this sequence, and the
      * {@code char} value at the following index is in the
      * low-surrogate range, then the supplementary code point
      * corresponding to this surrogate pair is returned. Otherwise,
      * the {@code char} value at the given index is returned.
      *
      * @param      index the index to the {@code char} values
      * @return     the code point value of the character at the
      *             {@code index}
-     * @exception  IndexOutOfBoundsException  if the {@code index}
+     * @throws     IndexOutOfBoundsException  if the {@code index}
      *             argument is negative or not less than the length of this
      *             sequence.
      */
     public int codePointAt(int index) {
-        if ((index < 0) || (index >= count)) {
-            throw new StringIndexOutOfBoundsException(index);
+        int count = this.count;
+        byte[] value = this.value;
+        checkIndex(index, count);
+        if (isLatin1()) {
+            return value[index] & 0xff;
         }
-        return Character.codePointAtImpl(value, index, count);
+        return StringUTF16.codePointAtSB(value, index, count);
     }
 
     /**
      * Returns the character (Unicode code point) before the specified
      * index. The index refers to {@code char} values
      * (Unicode code units) and ranges from {@code 1} to {@link
      * #length()}.
      *
      * <p> If the {@code char} value at {@code (index - 1)}
      * is in the low-surrogate range, {@code (index - 2)} is not
      * negative, and the {@code char} value at {@code (index -
      * 2)} is in the high-surrogate range, then the
      * supplementary code point value of the surrogate pair is
      * returned. If the {@code char} value at {@code index -
      * 1} is an unpaired low-surrogate or a high-surrogate, the
      * surrogate value is returned.
      *
      * @param     index the index following the code point that should be returned
      * @return    the Unicode code point value before the given index.
-     * @exception IndexOutOfBoundsException if the {@code index}
+     * @throws    IndexOutOfBoundsException if the {@code index}
      *            argument is less than 1 or greater than the length
      *            of this sequence.
      */
     public int codePointBefore(int index) {
         int i = index - 1;
-        if ((i < 0) || (i >= count)) {
+        if (i < 0 || i >= count) {
             throw new StringIndexOutOfBoundsException(index);
         }
-        return Character.codePointBeforeImpl(value, index, 0);
+        if (isLatin1()) {
+            return value[i] & 0xff;
+        }
+        return StringUTF16.codePointBeforeSB(value, index);
     }
 
     /**
      * Returns the number of Unicode code points in the specified text
      * range of this sequence. The text range begins at the specified
      * {@code beginIndex} and extends to the {@code char} at
      * index {@code endIndex - 1}. Thus the length (in
      * {@code char}s) of the text range is
      * {@code endIndex-beginIndex}. Unpaired surrogates within
      * this sequence count as one code point each.
      *
      * @param beginIndex the index to the first {@code char} of
      * the text range.
      * @param endIndex the index after the last {@code char} of
      * the text range.
      * @return the number of Unicode code points in the specified text
      * range
-     * @exception IndexOutOfBoundsException if the
+     * @throws    IndexOutOfBoundsException if the
      * {@code beginIndex} is negative, or {@code endIndex}
      * is larger than the length of this sequence, or
      * {@code beginIndex} is larger than {@code endIndex}.
      */
     public int codePointCount(int beginIndex, int endIndex) {
         if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {
             throw new IndexOutOfBoundsException();
         }
-        return Character.codePointCountImpl(value, beginIndex, endIndex-beginIndex);
+        if (isLatin1()) {
+            return endIndex - beginIndex;
+        }
+        return StringUTF16.codePointCountSB(value, beginIndex, endIndex);
     }
 
     /**
      * Returns the index within this sequence that is offset from the
      * given {@code index} by {@code codePointOffset} code
      * points. Unpaired surrogates within the text range given by
      * {@code index} and {@code codePointOffset} count as
      * one code point each.
      *
      * @param index the index to be offset
      * @param codePointOffset the offset in code points
      * @return the index within this sequence
-     * @exception IndexOutOfBoundsException if {@code index}
+     * @throws    IndexOutOfBoundsException if {@code index}
      *   is negative or larger then the length of this sequence,
      *   or if {@code codePointOffset} is positive and the subsequence
      *   starting with {@code index} has fewer than
      *   {@code codePointOffset} code points,
      *   or if {@code codePointOffset} is negative and the subsequence
      *   before {@code index} has fewer than the absolute value of
      *   {@code codePointOffset} code points.
      */
     public int offsetByCodePoints(int index, int codePointOffset) {
         if (index < 0 || index > count) {
             throw new IndexOutOfBoundsException();
         }
-        return Character.offsetByCodePointsImpl(value, 0, count,
-                                                index, codePointOffset);
+        return Character.offsetByCodePoints(this,
+                                            index, codePointOffset);
     }
 
     /**
      * Characters are copied from this sequence into the
      * destination character array {@code dst}. The first character to
      * be copied is at index {@code srcBegin}; the last character to
      * be copied is at index {@code srcEnd-1}. The total number of
      * characters to be copied is {@code srcEnd-srcBegin}. The
      * characters are copied into the subarray of {@code dst} starting
      * at index {@code dstBegin} and ending at index:
      * <pre>{@code
      * dstbegin + (srcEnd-srcBegin) - 1
      * }</pre>
      *
      * @param      srcBegin   start copying at this offset.
      * @param      srcEnd     stop copying at this offset.
      * @param      dst        the array to copy the data into.
      * @param      dstBegin   offset into {@code dst}.
      * @throws     IndexOutOfBoundsException  if any of the following is true:
      *             <ul>
      *             <li>{@code srcBegin} is negative
      *             <li>{@code dstBegin} is negative
      *             <li>the {@code srcBegin} argument is greater than
      *             the {@code srcEnd} argument.
      *             <li>{@code srcEnd} is greater than
      *             {@code this.length()}.
      *             <li>{@code dstBegin+srcEnd-srcBegin} is greater than
      *             {@code dst.length}
      *             </ul>
      */
     public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
     {
-        if (srcBegin < 0)
-            throw new StringIndexOutOfBoundsException(srcBegin);
-        if ((srcEnd < 0) || (srcEnd > count))
-            throw new StringIndexOutOfBoundsException(srcEnd);
-        if (srcBegin > srcEnd)
-            throw new StringIndexOutOfBoundsException("srcBegin > srcEnd");
-        System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
+        checkRangeSIOOBE(srcBegin, srcEnd, count);  // compatible to old version
+        int n = srcEnd - srcBegin;
+        checkRange(dstBegin, dstBegin + n, dst.length);
+        if (isLatin1()) {
+            StringLatin1.getChars(value, srcBegin, srcEnd, dst, dstBegin);
+        } else {
+            StringUTF16.getChars(value, srcBegin, srcEnd, dst, dstBegin);
+        }
     }
 
     /**
      * The character at the specified index is set to {@code ch}. This
      * sequence is altered to represent a new character sequence that is
      * identical to the old character sequence, except that it contains the
      * character {@code ch} at position {@code index}.
      * <p>
      * The index argument must be greater than or equal to
      * {@code 0}, and less than the length of this sequence.
      *
      * @param      index   the index of the character to modify.
      * @param      ch      the new character.
      * @throws     IndexOutOfBoundsException  if {@code index} is
      *             negative or greater than or equal to {@code length()}.
      */
     public void setCharAt(int index, char ch) {
-        if ((index < 0) || (index >= count))
-            throw new StringIndexOutOfBoundsException(index);
-        value[index] = ch;
+        checkIndex(index, count);
+        if (isLatin1() && StringLatin1.canEncode(ch)) {
+            value[index] = (byte)ch;
+        } else {
+            if (isLatin1()) {
+                inflate();
+            }
+            StringUTF16.putCharSB(value, index, ch);
+        }
     }
 
     /**
      * Appends the string representation of the {@code Object} argument.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(Object)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   obj   an {@code Object}.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(Object obj) {
         return append(String.valueOf(obj));
     }
 
     /**
      * Appends the specified string to this character sequence.
      * <p>
      * The characters of the {@code String} argument are appended, in
      * order, increasing the length of this sequence by the length of the
      * argument. If {@code str} is {@code null}, then the four
      * characters {@code "null"} are appended.
      * <p>
      * Let <i>n</i> be the length of this character sequence just prior to
      * execution of the {@code append} method. Then the character at
      * index <i>k</i> in the new character sequence is equal to the character
      * at index <i>k</i> in the old character sequence, if <i>k</i> is less
      * than <i>n</i>; otherwise, it is equal to the character at index
      * <i>k-n</i> in the argument {@code str}.
      *
      * @param   str   a string.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(String str) {
-        if (str == null)
+        if (str == null) {
             return appendNull();
+        }
         int len = str.length();
         ensureCapacityInternal(count + len);
-        str.getChars(0, len, value, count);
+        putStringAt(count, str);
         count += len;
         return this;
     }
 
     // Documentation in subclasses because of synchro difference
     public AbstractStringBuilder append(StringBuffer sb) {
-        if (sb == null)
-            return appendNull();
-        int len = sb.length();
-        ensureCapacityInternal(count + len);
-        sb.getChars(0, len, value, count);
-        count += len;
-        return this;
+        return this.append((AbstractStringBuilder)sb);
     }
 
     /**
      * @since 1.8
      */
     AbstractStringBuilder append(AbstractStringBuilder asb) {
-        if (asb == null)
+        if (asb == null) {
             return appendNull();
+        }
         int len = asb.length();
         ensureCapacityInternal(count + len);
-        asb.getChars(0, len, value, count);
+        if (getCoder() != asb.getCoder()) {
+            inflate();
+        }
+        asb.getBytes(value, count, coder);
         count += len;
         return this;
     }
 
     // Documentation in subclasses because of synchro difference
     @Override
     public AbstractStringBuilder append(CharSequence s) {
-        if (s == null)
+        if (s == null) {
             return appendNull();
-        if (s instanceof String)
+        }
+        if (s instanceof String) {
             return this.append((String)s);
-        if (s instanceof AbstractStringBuilder)
+        }
+        if (s instanceof AbstractStringBuilder) {
             return this.append((AbstractStringBuilder)s);
-
+        }
         return this.append(s, 0, s.length());
     }
 
     private AbstractStringBuilder appendNull() {
-        int c = count;
-        ensureCapacityInternal(c + 4);
-        final char[] value = this.value;
-        value[c++] = 'n';
-        value[c++] = 'u';
-        value[c++] = 'l';
-        value[c++] = 'l';
-        count = c;
+        ensureCapacityInternal(count + 4);
+        int count = this.count;
+        byte[] val = this.value;
+        if (isLatin1()) {
+            val[count++] = 'n';
+            val[count++] = 'u';
+            val[count++] = 'l';
+            val[count++] = 'l';
+        } else {
+            count = StringUTF16.putCharsAt(val, count, 'n', 'u', 'l', 'l');
+        }
+        this.count = count;
         return this;
     }
 
     /**
      * Appends a subsequence of the specified {@code CharSequence} to this
      * sequence.
      * <p>
      * Characters of the argument {@code s}, starting at
      * index {@code start}, are appended, in order, to the contents of
      * this sequence up to the (exclusive) index {@code end}. The length
      * of this sequence is increased by the value of {@code end - start}.
      * <p>
      * Let <i>n</i> be the length of this character sequence just prior to
      * execution of the {@code append} method. Then the character at
      * index <i>k</i> in this character sequence becomes equal to the
      * character at index <i>k</i> in this sequence, if <i>k</i> is less than
      * <i>n</i>; otherwise, it is equal to the character at index
      * <i>k+start-n</i> in the argument {@code s}.
      * <p>
      * If {@code s} is {@code null}, then this method appends
      * characters as if the s parameter was a sequence containing the four
      * characters {@code "null"}.
      *
      * @param   s the sequence to append.
      * @param   start   the starting index of the subsequence to be appended.
      * @param   end     the end index of the subsequence to be appended.
      * @return  a reference to this object.
      * @throws     IndexOutOfBoundsException if
      *             {@code start} is negative, or
      *             {@code start} is greater than {@code end} or
      *             {@code end} is greater than {@code s.length()}
      */
     @Override
     public AbstractStringBuilder append(CharSequence s, int start, int end) {
-        if (s == null)
+        if (s == null) {
             s = "null";
-        if ((start < 0) || (start > end) || (end > s.length()))
-            throw new IndexOutOfBoundsException(
-                "start " + start + ", end " + end + ", s.length() "
-                + s.length());
+        }
+        checkRange(start, end, s.length());
         int len = end - start;
         ensureCapacityInternal(count + len);
-        for (int i = start, j = count; i < end; i++, j++)
-            value[j] = s.charAt(i);
-        count += len;
+        appendChars(s, start, end);
         return this;
     }
 
     /**
      * Appends the string representation of the {@code char} array
      * argument to this sequence.
      * <p>
      * The characters of the array argument are appended, in order, to
      * the contents of this sequence. The length of this sequence
      * increases by the length of the argument.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(char[])},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   str   the characters to be appended.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(char[] str) {
         int len = str.length;
         ensureCapacityInternal(count + len);
-        System.arraycopy(str, 0, value, count, len);
-        count += len;
+        appendChars(str, 0, len);
         return this;
     }
 
     /**
      * Appends the string representation of a subarray of the
      * {@code char} array argument to this sequence.
      * <p>
      * Characters of the {@code char} array {@code str}, starting at
      * index {@code offset}, are appended, in order, to the contents
      * of this sequence. The length of this sequence increases
      * by the value of {@code len}.
      * <p>
      * The overall effect is exactly as if the arguments were converted
      * to a string by the method {@link String#valueOf(char[],int,int)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   str      the characters to be appended.
      * @param   offset   the index of the first {@code char} to append.
      * @param   len      the number of {@code char}s to append.
      * @return  a reference to this object.
      * @throws IndexOutOfBoundsException
      *         if {@code offset < 0} or {@code len < 0}
      *         or {@code offset+len > str.length}
      */
     public AbstractStringBuilder append(char str[], int offset, int len) {
-        if (len > 0)                // let arraycopy report AIOOBE for len < 0
-            ensureCapacityInternal(count + len);
-        System.arraycopy(str, offset, value, count, len);
-        count += len;
+        int end = offset + len;
+        checkRange(offset, end, str.length);
+        ensureCapacityInternal(count + len);
+        appendChars(str, offset, end);
         return this;
     }
 
     /**
      * Appends the string representation of the {@code boolean}
      * argument to the sequence.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(boolean)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   b   a {@code boolean}.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(boolean b) {
-        if (b) {
-            ensureCapacityInternal(count + 4);
-            value[count++] = 't';
-            value[count++] = 'r';
-            value[count++] = 'u';
-            value[count++] = 'e';
+        ensureCapacityInternal(count + (b ? 4 : 5));
+        int count = this.count;
+        byte[] val = this.value;
+        if (isLatin1()) {
+            if (b) {
+                val[count++] = 't';
+                val[count++] = 'r';
+                val[count++] = 'u';
+                val[count++] = 'e';
+            } else {
+                val[count++] = 'f';
+                val[count++] = 'a';
+                val[count++] = 'l';
+                val[count++] = 's';
+                val[count++] = 'e';
+            }
         } else {
-            ensureCapacityInternal(count + 5);
-            value[count++] = 'f';
-            value[count++] = 'a';
-            value[count++] = 'l';
-            value[count++] = 's';
-            value[count++] = 'e';
+            if (b) {
+                count = StringUTF16.putCharsAt(val, count, 't', 'r', 'u', 'e');
+            } else {
+                count = StringUTF16.putCharsAt(val, count, 'f', 'a', 'l', 's', 'e');
+            }
         }
+        this.count = count;
         return this;
     }
 
     /**
      * Appends the string representation of the {@code char}
      * argument to this sequence.
      * <p>
      * The argument is appended to the contents of this sequence.
      * The length of this sequence increases by {@code 1}.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(char)},
      * and the character in that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   c   a {@code char}.
      * @return  a reference to this object.
      */
     @Override
     public AbstractStringBuilder append(char c) {
         ensureCapacityInternal(count + 1);
-        value[count++] = c;
+        if (isLatin1() && StringLatin1.canEncode(c)) {
+            value[count++] = (byte)c;
+        } else {
+            if (isLatin1()) {
+                inflate();
+            }
+            StringUTF16.putCharSB(value, count++, c);
+        }
         return this;
     }
 
     /**
      * Appends the string representation of the {@code int}
      * argument to this sequence.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(int)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   i   an {@code int}.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(int i) {
-        if (i == Integer.MIN_VALUE) {
-            append("-2147483648");
-            return this;
-        }
-        int appendedLength = (i < 0) ? Integer.stringSize(-i) + 1
-                                     : Integer.stringSize(i);
-        int spaceNeeded = count + appendedLength;
+        int count = this.count;
+        int spaceNeeded = count + Integer.stringSize(i);
         ensureCapacityInternal(spaceNeeded);
-        Integer.getChars(i, spaceNeeded, value);
-        count = spaceNeeded;
+        if (isLatin1()) {
+            Integer.getChars(i, spaceNeeded, value);
+        } else {
+            StringUTF16.getChars(i, count, spaceNeeded, value);
+        }
+        this.count = spaceNeeded;
         return this;
     }
 
     /**
      * Appends the string representation of the {@code long}
      * argument to this sequence.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(long)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   l   a {@code long}.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(long l) {
-        if (l == Long.MIN_VALUE) {
-            append("-9223372036854775808");
-            return this;
-        }
-        int appendedLength = (l < 0) ? Long.stringSize(-l) + 1
-                                     : Long.stringSize(l);
-        int spaceNeeded = count + appendedLength;
+        int count = this.count;
+        int spaceNeeded = count + Long.stringSize(l);
         ensureCapacityInternal(spaceNeeded);
-        Long.getChars(l, spaceNeeded, value);
-        count = spaceNeeded;
+        if (isLatin1()) {
+            Long.getChars(l, spaceNeeded, value);
+        } else {
+            StringUTF16.getChars(l, count, spaceNeeded, value);
+        }
+        this.count = spaceNeeded;
         return this;
     }
 
     /**
      * Appends the string representation of the {@code float}
      * argument to this sequence.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(float)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   f   a {@code float}.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(float f) {
         FloatingDecimal.appendTo(f,this);
         return this;
     }
 
     /**
      * Appends the string representation of the {@code double}
      * argument to this sequence.
      * <p>
      * The overall effect is exactly as if the argument were converted
      * to a string by the method {@link String#valueOf(double)},
      * and the characters of that string were then
      * {@link #append(String) appended} to this character sequence.
      *
      * @param   d   a {@code double}.
      * @return  a reference to this object.
      */
     public AbstractStringBuilder append(double d) {
         FloatingDecimal.appendTo(d,this);
         return this;
     }
 
     /**
      * Removes the characters in a substring of this sequence.
      * The substring begins at the specified {@code start} and extends to
      * the character at index {@code end - 1} or to the end of the
      * sequence if no such character exists. If
      * {@code start} is equal to {@code end}, no changes are made.
      *
      * @param      start  The beginning index, inclusive.
      * @param      end    The ending index, exclusive.
      * @return     This object.
      * @throws     StringIndexOutOfBoundsException  if {@code start}
      *             is negative, greater than {@code length()}, or
      *             greater than {@code end}.
      */
     public AbstractStringBuilder delete(int start, int end) {
-        if (start < 0)
-            throw new StringIndexOutOfBoundsException(start);
-        if (end > count)
+        int count = this.count;
+        if (end > count) {
             end = count;
-        if (start > end)
-            throw new StringIndexOutOfBoundsException();
+        }
+        checkRangeSIOOBE(start, end, count);
         int len = end - start;
         if (len > 0) {
-            System.arraycopy(value, start+len, value, start, count-end);
-            count -= len;
+            shift(end, -len);
+            this.count = count - len;
         }
         return this;
     }
 
     /**
      * Appends the string representation of the {@code codePoint}
      * argument to this sequence.
      *
      * <p> The argument is appended to the contents of this sequence.
      * The length of this sequence increases by
      * {@link Character#charCount(int) Character.charCount(codePoint)}.
      *
      * <p> The overall effect is exactly as if the argument were
      * converted to a {@code char} array by the method
      * {@link Character#toChars(int)} and the character in that array
      * were then {@link #append(char[]) appended} to this character
      * sequence.
      *
      * @param   codePoint   a Unicode code point
      * @return  a reference to this object.
-     * @exception IllegalArgumentException if the specified
+     * @throws    IllegalArgumentException if the specified
      * {@code codePoint} isn't a valid Unicode code point
      */
     public AbstractStringBuilder appendCodePoint(int codePoint) {
-        final int count = this.count;
-
         if (Character.isBmpCodePoint(codePoint)) {
-            ensureCapacityInternal(count + 1);
-            value[count] = (char) codePoint;
-            this.count = count + 1;
-        } else if (Character.isValidCodePoint(codePoint)) {
-            ensureCapacityInternal(count + 2);
-            Character.toSurrogates(codePoint, value, count);
-            this.count = count + 2;
-        } else {
-            throw new IllegalArgumentException();
+            return append((char)codePoint);
         }
-        return this;
+        return append(Character.toChars(codePoint));
     }
 
     /**
      * Removes the {@code char} at the specified position in this
      * sequence. This sequence is shortened by one {@code char}.
      *
      * <p>Note: If the character at the given index is a supplementary
      * character, this method does not remove the entire character. If
      * correct handling of supplementary characters is required,
      * determine the number of {@code char}s to remove by calling
      * {@code Character.charCount(thisSequence.codePointAt(index))},
      * where {@code thisSequence} is this sequence.
      *
      * @param       index  Index of {@code char} to remove
      * @return      This object.
      * @throws      StringIndexOutOfBoundsException  if the {@code index}
      *              is negative or greater than or equal to
      *              {@code length()}.
      */
     public AbstractStringBuilder deleteCharAt(int index) {
-        if ((index < 0) || (index >= count))
-            throw new StringIndexOutOfBoundsException(index);
-        System.arraycopy(value, index+1, value, index, count-index-1);
+        checkIndex(index, count);
+        shift(index + 1, -1);
         count--;
         return this;
     }
 
     /**
      * Replaces the characters in a substring of this sequence
      * with characters in the specified {@code String}. The substring
      * begins at the specified {@code start} and extends to the character
      * at index {@code end - 1} or to the end of the
      * sequence if no such character exists. First the
      * characters in the substring are removed and then the specified
      * {@code String} is inserted at {@code start}. (This
      * sequence will be lengthened to accommodate the
      * specified String if necessary.)
      *
      * @param      start    The beginning index, inclusive.
      * @param      end      The ending index, exclusive.
      * @param      str   String that will replace previous contents.
      * @return     This object.
      * @throws     StringIndexOutOfBoundsException  if {@code start}
      *             is negative, greater than {@code length()}, or
      *             greater than {@code end}.
      */
     public AbstractStringBuilder replace(int start, int end, String str) {
-        if (start < 0)
-            throw new StringIndexOutOfBoundsException(start);
-        if (start > count)
-            throw new StringIndexOutOfBoundsException("start > length()");
-        if (start > end)
-            throw new StringIndexOutOfBoundsException("start > end");
-
-        if (end > count)
+        int count = this.count;
+        if (end > count) {
             end = count;
+        }
+        checkRangeSIOOBE(start, end, count);
         int len = str.length();
         int newCount = count + len - (end - start);
         ensureCapacityInternal(newCount);
-
-        System.arraycopy(value, end, value, start + len, count - end);
-        str.getChars(value, start);
-        count = newCount;
+        shift(end, newCount - count);
+        this.count = newCount;
+        putStringAt(start, str);
         return this;
     }
 
     /**
      * Returns a new {@code String} that contains a subsequence of
      * characters currently contained in this character sequence. The
      * substring begins at the specified index and extends to the end of
      * this sequence.
      *
      * @param      start    The beginning index, inclusive.
      * @return     The new string.
      * @throws     StringIndexOutOfBoundsException  if {@code start} is
      *             less than zero, or greater than the length of this object.
      */
     public String substring(int start) {
         return substring(start, count);
     }
 
     /**
      * Returns a new character sequence that is a subsequence of this sequence.
      *
      * <p> An invocation of this method of the form
      *
      * <pre>{@code
      * sb.subSequence(begin,&nbsp;end)}</pre>
      *
      * behaves in exactly the same way as the invocation
      *
      * <pre>{@code
      * sb.substring(begin,&nbsp;end)}</pre>
      *
      * This method is provided so that this class can
      * implement the {@link CharSequence} interface.
      *
      * @param      start   the start index, inclusive.
      * @param      end     the end index, exclusive.
      * @return     the specified subsequence.
      *
      * @throws  IndexOutOfBoundsException
      *          if {@code start} or {@code end} are negative,
      *          if {@code end} is greater than {@code length()},
      *          or if {@code start} is greater than {@code end}
      * @spec JSR-51
      */
     @Override
     public CharSequence subSequence(int start, int end) {
         return substring(start, end);
     }
 
     /**
      * Returns a new {@code String} that contains a subsequence of
      * characters currently contained in this sequence. The
      * substring begins at the specified {@code start} and
      * extends to the character at index {@code end - 1}.
      *
      * @param      start    The beginning index, inclusive.
      * @param      end      The ending index, exclusive.
      * @return     The new string.
      * @throws     StringIndexOutOfBoundsException  if {@code start}
      *             or {@code end} are negative or greater than
      *             {@code length()}, or {@code start} is
      *             greater than {@code end}.
      */
     public String substring(int start, int end) {
-        if (start < 0)
-            throw new StringIndexOutOfBoundsException(start);
-        if (end > count)
-            throw new StringIndexOutOfBoundsException(end);
-        if (start > end)
-            throw new StringIndexOutOfBoundsException(end - start);
-        return new String(value, start, end - start);
+        checkRangeSIOOBE(start, end, count);
+        if (isLatin1()) {
+            return StringLatin1.newString(value, start, end - start);
+        }
+        return StringUTF16.newString(value, start, end - start);
+    }
+
+    private void shift(int offset, int n) {
+        System.arraycopy(value, offset << coder,
+                         value, (offset + n) << coder, (count - offset) << coder);
     }
 
     /**
      * Inserts the string representation of a subarray of the {@code str}
      * array argument into this sequence. The subarray begins at the
      * specified {@code offset} and extends {@code len} {@code char}s.
      * The characters of the subarray are inserted into this sequence at
      * the position indicated by {@code index}. The length of this
      * sequence increases by {@code len} {@code char}s.
      *
      * @param      index    position at which to insert subarray.
      * @param      str       A {@code char} array.
      * @param      offset   the index of the first {@code char} in subarray to
      *             be inserted.
      * @param      len      the number of {@code char}s in the subarray to
      *             be inserted.
      * @return     This object
      * @throws     StringIndexOutOfBoundsException  if {@code index}
      *             is negative or greater than {@code length()}, or
      *             {@code offset} or {@code len} are negative, or
      *             {@code (offset+len)} is greater than
      *             {@code str.length}.
      */
     public AbstractStringBuilder insert(int index, char[] str, int offset,
                                         int len)
     {
-        if ((index < 0) || (index > length()))
-            throw new StringIndexOutOfBoundsException(index);
-        if ((offset < 0) || (len < 0) || (offset > str.length - len))
-            throw new StringIndexOutOfBoundsException(
-                "offset " + offset + ", len " + len + ", str.length "
-                + str.length);
+        checkOffset(index, count);
+        checkRangeSIOOBE(offset, offset + len, str.length);
         ensureCapacityInternal(count + len);
-        System.arraycopy(value, index, value, index + len, count - index);
-        System.arraycopy(str, offset, value, index, len);
+        shift(index, len);
         count += len;
+        putCharsAt(index, str, offset, offset + len);
         return this;
     }
 
     /**
      * Inserts the string representation of the {@code Object}
      * argument into this character sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(Object)},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      obj      an {@code Object}.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, Object obj) {
         return insert(offset, String.valueOf(obj));
     }
 
     /**
      * Inserts the string into this character sequence.
      * <p>
      * The characters of the {@code String} argument are inserted, in
      * order, into this sequence at the indicated offset, moving up any
      * characters originally above that position and increasing the length
      * of this sequence by the length of the argument. If
      * {@code str} is {@code null}, then the four characters
      * {@code "null"} are inserted into this sequence.
      * <p>
      * The character at index <i>k</i> in the new character sequence is
      * equal to:
      * <ul>
      * <li>the character at index <i>k</i> in the old character sequence, if
      * <i>k</i> is less than {@code offset}
      * <li>the character at index <i>k</i>{@code -offset} in the
      * argument {@code str}, if <i>k</i> is not less than
      * {@code offset} but is less than {@code offset+str.length()}
      * <li>the character at index <i>k</i>{@code -str.length()} in the
      * old character sequence, if <i>k</i> is not less than
      * {@code offset+str.length()}
      * </ul><p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      str      a string.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, String str) {
-        if ((offset < 0) || (offset > length()))
-            throw new StringIndexOutOfBoundsException(offset);
-        if (str == null)
+        checkOffset(offset, count);
+        if (str == null) {
             str = "null";
+        }
         int len = str.length();
         ensureCapacityInternal(count + len);
-        System.arraycopy(value, offset, value, offset + len, count - offset);
-        str.getChars(value, offset);
+        shift(offset, len);
         count += len;
+        putStringAt(offset, str);
         return this;
     }
 
     /**
      * Inserts the string representation of the {@code char} array
      * argument into this sequence.
      * <p>
      * The characters of the array argument are inserted into the
      * contents of this sequence at the position indicated by
      * {@code offset}. The length of this sequence increases by
      * the length of the argument.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(char[])},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      str      a character array.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, char[] str) {
-        if ((offset < 0) || (offset > length()))
-            throw new StringIndexOutOfBoundsException(offset);
+        checkOffset(offset, count);
         int len = str.length;
         ensureCapacityInternal(count + len);
-        System.arraycopy(value, offset, value, offset + len, count - offset);
-        System.arraycopy(str, 0, value, offset, len);
+        shift(offset, len);
         count += len;
+        putCharsAt(offset, str, 0, len);
         return this;
     }
 
     /**
      * Inserts the specified {@code CharSequence} into this sequence.
      * <p>
      * The characters of the {@code CharSequence} argument are inserted,
      * in order, into this sequence at the indicated offset, moving up
      * any characters originally above that position and increasing the length
      * of this sequence by the length of the argument s.
      * <p>
      * The result of this method is exactly the same as if it were an
      * invocation of this object's
      * {@link #insert(int,CharSequence,int,int) insert}(dstOffset, s, 0, s.length())
      * method.
      *
      * <p>If {@code s} is {@code null}, then the four characters
      * {@code "null"} are inserted into this sequence.
      *
      * @param      dstOffset   the offset.
      * @param      s the sequence to be inserted
      * @return     a reference to this object.
      * @throws     IndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int dstOffset, CharSequence s) {
-        if (s == null)
+        if (s == null) {
             s = "null";
-        if (s instanceof String)
+        }
+        if (s instanceof String) {
             return this.insert(dstOffset, (String)s);
+        }
         return this.insert(dstOffset, s, 0, s.length());
     }
 
     /**
      * Inserts a subsequence of the specified {@code CharSequence} into
      * this sequence.
      * <p>
      * The subsequence of the argument {@code s} specified by
      * {@code start} and {@code end} are inserted,
      * in order, into this sequence at the specified destination offset, moving
      * up any characters originally above that position. The length of this
      * sequence is increased by {@code end - start}.
      * <p>
      * The character at index <i>k</i> in this sequence becomes equal to:
      * <ul>
      * <li>the character at index <i>k</i> in this sequence, if
      * <i>k</i> is less than {@code dstOffset}
      * <li>the character at index <i>k</i>{@code +start-dstOffset} in
      * the argument {@code s}, if <i>k</i> is greater than or equal to
      * {@code dstOffset} but is less than {@code dstOffset+end-start}
      * <li>the character at index <i>k</i>{@code -(end-start)} in this
      * sequence, if <i>k</i> is greater than or equal to
      * {@code dstOffset+end-start}
      * </ul><p>
      * The {@code dstOffset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      * <p>The start argument must be nonnegative, and not greater than
      * {@code end}.
      * <p>The end argument must be greater than or equal to
      * {@code start}, and less than or equal to the length of s.
      *
      * <p>If {@code s} is {@code null}, then this method inserts
      * characters as if the s parameter was a sequence containing the four
      * characters {@code "null"}.
      *
      * @param      dstOffset   the offset in this sequence.
      * @param      s       the sequence to be inserted.
      * @param      start   the starting index of the subsequence to be inserted.
      * @param      end     the end index of the subsequence to be inserted.
      * @return     a reference to this object.
      * @throws     IndexOutOfBoundsException  if {@code dstOffset}
      *             is negative or greater than {@code this.length()}, or
      *              {@code start} or {@code end} are negative, or
      *              {@code start} is greater than {@code end} or
      *              {@code end} is greater than {@code s.length()}
      */
-     public AbstractStringBuilder insert(int dstOffset, CharSequence s,
-                                         int start, int end) {
-        if (s == null)
+    public AbstractStringBuilder insert(int dstOffset, CharSequence s,
+                                        int start, int end)
+    {
+        if (s == null) {
             s = "null";
-        if ((dstOffset < 0) || (dstOffset > this.length()))
-            throw new IndexOutOfBoundsException("dstOffset "+dstOffset);
-        if ((start < 0) || (end < 0) || (start > end) || (end > s.length()))
-            throw new IndexOutOfBoundsException(
-                "start " + start + ", end " + end + ", s.length() "
-                + s.length());
+        }
+        checkOffset(dstOffset, count);
+        checkRange(start, end, s.length());
         int len = end - start;
         ensureCapacityInternal(count + len);
-        System.arraycopy(value, dstOffset, value, dstOffset + len,
-                         count - dstOffset);
-        for (int i=start; i<end; i++)
-            value[dstOffset++] = s.charAt(i);
+        shift(dstOffset, len);
         count += len;
+        putCharsAt(dstOffset, s, start, end);
         return this;
     }
 
     /**
      * Inserts the string representation of the {@code boolean}
      * argument into this sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(boolean)},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      b        a {@code boolean}.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, boolean b) {
         return insert(offset, String.valueOf(b));
     }
 
     /**
      * Inserts the string representation of the {@code char}
      * argument into this sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(char)},
      * and the character in that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      c        a {@code char}.
      * @return     a reference to this object.
      * @throws     IndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, char c) {
+        checkOffset(offset, count);
         ensureCapacityInternal(count + 1);
-        System.arraycopy(value, offset, value, offset + 1, count - offset);
-        value[offset] = c;
+        shift(offset, 1);
         count += 1;
+        if (isLatin1() && StringLatin1.canEncode(c)) {
+            value[offset] = (byte)c;
+        } else {
+            if (isLatin1()) {
+                inflate();
+            }
+            StringUTF16.putCharSB(value, offset, c);
+        }
         return this;
     }
 
     /**
      * Inserts the string representation of the second {@code int}
      * argument into this sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(int)},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      i        an {@code int}.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, int i) {
         return insert(offset, String.valueOf(i));
     }
 
     /**
      * Inserts the string representation of the {@code long}
      * argument into this sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(long)},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      l        a {@code long}.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, long l) {
         return insert(offset, String.valueOf(l));
     }
 
     /**
      * Inserts the string representation of the {@code float}
      * argument into this sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(float)},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      f        a {@code float}.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, float f) {
         return insert(offset, String.valueOf(f));
     }
 
     /**
      * Inserts the string representation of the {@code double}
      * argument into this sequence.
      * <p>
      * The overall effect is exactly as if the second argument were
      * converted to a string by the method {@link String#valueOf(double)},
      * and the characters of that string were then
      * {@link #insert(int,String) inserted} into this character
      * sequence at the indicated offset.
      * <p>
      * The {@code offset} argument must be greater than or equal to
      * {@code 0}, and less than or equal to the {@linkplain #length() length}
      * of this sequence.
      *
      * @param      offset   the offset.
      * @param      d        a {@code double}.
      * @return     a reference to this object.
      * @throws     StringIndexOutOfBoundsException  if the offset is invalid.
      */
     public AbstractStringBuilder insert(int offset, double d) {
         return insert(offset, String.valueOf(d));
     }
 
     /**
      * Returns the index within this string of the first occurrence of the
-     * specified substring. The integer returned is the smallest value
-     * <i>k</i> such that:
-     * <pre>{@code
-     * this.toString().startsWith(str, <i>k</i>)
-     * }</pre>
-     * is {@code true}.
+     * specified substring.
      *
-     * @param   str   any string.
-     * @return  if the string argument occurs as a substring within this
-     *          object, then the index of the first character of the first
-     *          such substring is returned; if it does not occur as a
-     *          substring, {@code -1} is returned.
+     * <p>The returned index is the smallest value {@code k} for which:
+     * <pre>{@code
+     * this.toString().startsWith(str, k)
+     * }</pre>
+     * If no such value of {@code k} exists, then {@code -1} is returned.
+     *
+     * @param   str   the substring to search for.
+     * @return  the index of the first occurrence of the specified substring,
+     *          or {@code -1} if there is no such occurrence.
      */
     public int indexOf(String str) {
         return indexOf(str, 0);
     }
 
     /**
      * Returns the index within this string of the first occurrence of the
-     * specified substring, starting at the specified index.  The integer
-     * returned is the smallest value {@code k} for which:
+     * specified substring, starting at the specified index.
+     *
+     * <p>The returned index is the smallest value {@code k} for which:
      * <pre>{@code
      *     k >= Math.min(fromIndex, this.length()) &&
      *                   this.toString().startsWith(str, k)
      * }</pre>
-     * If no such value of <i>k</i> exists, then -1 is returned.
+     * If no such value of {@code k} exists, then {@code -1} is returned.
      *
-     * @param   str         the substring for which to search.
+     * @param   str         the substring to search for.
      * @param   fromIndex   the index from which to start the search.
-     * @return  the index within this string of the first occurrence of the
-     *          specified substring, starting at the specified index.
+     * @return  the index of the first occurrence of the specified substring,
+     *          starting at the specified index,
+     *          or {@code -1} if there is no such occurrence.
      */
     public int indexOf(String str, int fromIndex) {
-        return String.indexOf(value, 0, count, str, fromIndex);
+        return String.indexOf(value, coder, count, str, fromIndex);
     }
 
     /**
-     * Returns the index within this string of the rightmost occurrence
-     * of the specified substring.  The rightmost empty string "" is
+     * Returns the index within this string of the last occurrence of the
+     * specified substring.  The last occurrence of the empty string "" is
      * considered to occur at the index value {@code this.length()}.
-     * The returned index is the largest value <i>k</i> such that
+     *
+     * <p>The returned index is the largest value {@code k} for which:
      * <pre>{@code
      * this.toString().startsWith(str, k)
      * }</pre>
-     * is true.
+     * If no such value of {@code k} exists, then {@code -1} is returned.
      *
      * @param   str   the substring to search for.
-     * @return  if the string argument occurs one or more times as a substring
-     *          within this object, then the index of the first character of
-     *          the last such substring is returned. If it does not occur as
-     *          a substring, {@code -1} is returned.
+     * @return  the index of the last occurrence of the specified substring,
+     *          or {@code -1} if there is no such occurrence.
      */
     public int lastIndexOf(String str) {
         return lastIndexOf(str, count);
     }
 
     /**
      * Returns the index within this string of the last occurrence of the
-     * specified substring. The integer returned is the largest value <i>k</i>
-     * such that:
+     * specified substring, searching backward starting at the specified index.
+     *
+     * <p>The returned index is the largest value {@code k} for which:
      * <pre>{@code
      *     k <= Math.min(fromIndex, this.length()) &&
      *                   this.toString().startsWith(str, k)
      * }</pre>
-     * If no such value of <i>k</i> exists, then -1 is returned.
+     * If no such value of {@code k} exists, then {@code -1} is returned.
      *
      * @param   str         the substring to search for.
      * @param   fromIndex   the index to start the search from.
-     * @return  the index within this sequence of the last occurrence of the
-     *          specified substring.
+     * @return  the index of the last occurrence of the specified substring,
+     *          searching backward from the specified index,
+     *          or {@code -1} if there is no such occurrence.
      */
     public int lastIndexOf(String str, int fromIndex) {
-        return String.lastIndexOf(value, 0, count, str, fromIndex);
+        return String.lastIndexOf(value, coder, count, str, fromIndex);
     }
 
     /**
      * Causes this character sequence to be replaced by the reverse of
      * the sequence. If there are any surrogate pairs included in the
      * sequence, these are treated as single characters for the
      * reverse operation. Thus, the order of the high-low surrogates
      * is never reversed.
      *
      * Let <i>n</i> be the character length of this character sequence
      * (not the length in {@code char} values) just prior to
      * execution of the {@code reverse} method. Then the
      * character at index <i>k</i> in the new character sequence is
      * equal to the character at index <i>n-k-1</i> in the old
      * character sequence.
      *
      * <p>Note that the reverse operation may result in producing
      * surrogate pairs that were unpaired low-surrogates and
      * high-surrogates before the operation. For example, reversing
      * "\u005CuDC00\u005CuD800" produces "\u005CuD800\u005CuDC00" which is
      * a valid surrogate pair.
      *
      * @return  a reference to this object.
      */
     public AbstractStringBuilder reverse() {
-        boolean hasSurrogates = false;
+        byte[] val = this.value;
+        int count = this.count;
+        int coder = this.coder;
         int n = count - 1;
-        for (int j = (n-1) >> 1; j >= 0; j--) {
-            int k = n - j;
-            char cj = value[j];
-            char ck = value[k];
-            value[j] = ck;
-            value[k] = cj;
-            if (Character.isSurrogate(cj) ||
-                Character.isSurrogate(ck)) {
-                hasSurrogates = true;
+        if (COMPACT_STRINGS && coder == LATIN1) {
+            for (int j = (n-1) >> 1; j >= 0; j--) {
+                int k = n - j;
+                byte cj = val[j];
+                val[j] = val[k];
+                val[k] = cj;
             }
-        }
-        if (hasSurrogates) {
-            reverseAllValidSurrogatePairs();
+        } else {
+            StringUTF16.reverse(val, count);
         }
         return this;
     }
 
-    /** Outlined helper method for reverse() */
-    private void reverseAllValidSurrogatePairs() {
-        for (int i = 0; i < count - 1; i++) {
-            char c2 = value[i];
-            if (Character.isLowSurrogate(c2)) {
-                char c1 = value[i + 1];
-                if (Character.isHighSurrogate(c1)) {
-                    value[i++] = c1;
-                    value[i] = c2;
-                }
-            }
-        }
-    }
-
     /**
      * Returns a string representing the data in this sequence.
      * A new {@code String} object is allocated and initialized to
      * contain the character sequence currently represented by this
      * object. This {@code String} is then returned. Subsequent
      * changes to this sequence do not affect the contents of the
      * {@code String}.
      *
      * @return  a string representation of this sequence of characters.
      */
     @Override
     public abstract String toString();
 
     /**
+     * {@inheritDoc}
+     * @since 9
+     */
+    @Override
+    public IntStream chars() {
+        // Reuse String-based spliterator. This requires a supplier to
+        // capture the value and count when the terminal operation is executed
+        return StreamSupport.intStream(
+                () -> {
+                    // The combined set of field reads are not atomic and thread
+                    // safe but bounds checks will ensure no unsafe reads from
+                    // the byte array
+                    byte[] val = this.value;
+                    int count = this.count;
+                    byte coder = this.coder;
+                    return coder == LATIN1
+                           ? new StringLatin1.CharsSpliterator(val, 0, count, 0)
+                           : new StringUTF16.CharsSpliterator(val, 0, count, 0);
+                },
+                Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED,
+                false);
+    }
+
+    /**
+     * {@inheritDoc}
+     * @since 9
+     */
+    @Override
+    public IntStream codePoints() {
+        // Reuse String-based spliterator. This requires a supplier to
+        // capture the value and count when the terminal operation is executed
+        return StreamSupport.intStream(
+                () -> {
+                    // The combined set of field reads are not atomic and thread
+                    // safe but bounds checks will ensure no unsafe reads from
+                    // the byte array
+                    byte[] val = this.value;
+                    int count = this.count;
+                    byte coder = this.coder;
+                    return coder == LATIN1
+                           ? new StringLatin1.CharsSpliterator(val, 0, count, 0)
+                           : new StringUTF16.CodePointsSpliterator(val, 0, count, 0);
+                },
+                Spliterator.ORDERED,
+                false);
+    }
+
+    /**
      * Needed by {@code String} for the contentEquals method.
      */
-    final char[] getValue() {
+    final byte[] getValue() {
         return value;
     }
 
+    /*
+     * Invoker guarantees it is in UTF16 (inflate itself for asb), if two
+     * coders are different and the dstBegin has enough space
+     *
+     * @param dstBegin  the char index, not offset of byte[]
+     * @param coder     the coder of dst[]
+     */
+    void getBytes(byte dst[], int dstBegin, byte coder) {
+        if (this.coder == coder) {
+            System.arraycopy(value, 0, dst, dstBegin << coder, count << coder);
+        } else {        // this.coder == LATIN && coder == UTF16
+            StringLatin1.inflate(value, 0, dst, dstBegin, count);
+        }
+    }
+
+    /* for readObject() */
+    void initBytes(char[] value, int off, int len) {
+        if (String.COMPACT_STRINGS) {
+            this.value = StringUTF16.compress(value, off, len);
+            if (this.value != null) {
+                this.coder = LATIN1;
+                return;
+            }
+        }
+        this.coder = UTF16;
+        this.value = StringUTF16.toBytes(value, off, len);
+    }
+
+    final byte getCoder() {
+        return COMPACT_STRINGS ? coder : UTF16;
+    }
+
+    final boolean isLatin1() {
+        return COMPACT_STRINGS && coder == LATIN1;
+    }
+
+    private final void putCharsAt(int index, char[] s, int off, int end) {
+        if (isLatin1()) {
+            byte[] val = this.value;
+            for (int i = off, j = index; i < end; i++) {
+                char c = s[i];
+                if (StringLatin1.canEncode(c)) {
+                    val[j++] = (byte)c;
+                } else {
+                    inflate();
+                    StringUTF16.putCharsSB(this.value, j, s, i, end);
+                    return;
+                }
+            }
+        } else {
+            StringUTF16.putCharsSB(this.value, index, s, off, end);
+        }
+    }
+
+    private final void putCharsAt(int index, CharSequence s, int off, int end) {
+        if (isLatin1()) {
+            byte[] val = this.value;
+            for (int i = off, j = index; i < end; i++) {
+                char c = s.charAt(i);
+                if (StringLatin1.canEncode(c)) {
+                    val[j++] = (byte)c;
+                } else {
+                    inflate();
+                    StringUTF16.putCharsSB(this.value, j, s, i, end);
+                    return;
+                }
+            }
+        } else {
+            StringUTF16.putCharsSB(this.value, index, s, off, end);
+        }
+    }
+
+    private final void putStringAt(int index, String str) {
+        if (getCoder() != str.coder()) {
+            inflate();
+        }
+        str.getBytes(value, index, coder);
+    }
+
+    private final void appendChars(char[] s, int off, int end) {
+        int count = this.count;
+        if (isLatin1()) {
+            byte[] val = this.value;
+            for (int i = off, j = count; i < end; i++) {
+                char c = s[i];
+                if (StringLatin1.canEncode(c)) {
+                    val[j++] = (byte)c;
+                } else {
+                    this.count = count = j;
+                    inflate();
+                    StringUTF16.putCharsSB(this.value, j, s, i, end);
+                    this.count = count + end - i;
+                    return;
+                }
+            }
+        } else {
+            StringUTF16.putCharsSB(this.value, count, s, off, end);
+        }
+        this.count = count + end - off;
+    }
+
+    private final void appendChars(CharSequence s, int off, int end) {
+        if (isLatin1()) {
+            byte[] val = this.value;
+            for (int i = off, j = count; i < end; i++) {
+                char c = s.charAt(i);
+                if (StringLatin1.canEncode(c)) {
+                    val[j++] = (byte)c;
+                } else {
+                    count = j;
+                    inflate();
+                    StringUTF16.putCharsSB(this.value, j, s, i, end);
+                    count += end - i;
+                    return;
+                }
+            }
+        } else {
+            StringUTF16.putCharsSB(this.value, count, s, off, end);
+        }
+        count += end - off;
+    }
+
+    /* IndexOutOfBoundsException, if out of bounds */
+    private static void checkRange(int start, int end, int len) {
+        if (start < 0 || start > end || end > len) {
+            throw new IndexOutOfBoundsException(
+                "start " + start + ", end " + end + ", length " + len);
+        }
+    }
+
+    /* StringIndexOutOfBoundsException, if out of bounds */
+    private static void checkRangeSIOOBE(int start, int end, int len) {
+        if (start < 0 || start > end || end > len) {
+            throw new StringIndexOutOfBoundsException(
+                "start " + start + ", end " + end + ", length " + len);
+        }
+    }
 }