https://openjdk.java.net/ 
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 * 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
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package java.awt.font;

import java.text.CharacterIterator;

class CharArrayIterator implements CharacterIterator {

    private char[] chars;
    private int pos;
    private int begin;

    CharArrayIterator(char[] chars) {

        reset(chars, 0);
    }

    CharArrayIterator(char[] chars, int begin) {

        reset(chars, begin);
    }

    
Sets the position to getBeginIndex() and returns the character at that
position.

See Also:
Returns:the first character in the text, or DONE if the text is empty
/**
     * Sets the position to getBeginIndex() and returns the character at that
     * position.
     * @return the first character in the text, or DONE if the text is empty
     * @see #getBeginIndex
     */
    public char first() {

        pos = 0;
        return current();
    }

    
Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty)
and returns the character at that position.

See Also:
Returns:the last character in the text, or DONE if the text is empty
/**
     * Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty)
     * and returns the character at that position.
     * @return the last character in the text, or DONE if the text is empty
     * @see #getEndIndex
     */
    public char last() {

        if (chars.length > 0) {
            pos = chars.length-1;
        }
        else {
            pos = 0;
        }
        return current();
    }

    
Gets the character at the current position (as returned by getIndex()).

See Also:
Returns:the character at the current position or DONE if the current
position is off the end of the text.
/**
     * Gets the character at the current position (as returned by getIndex()).
     * @return the character at the current position or DONE if the current
     * position is off the end of the text.
     * @see #getIndex
     */
    public char current() {

        if (pos >= 0 && pos < chars.length) {
            return chars[pos];
        }
        else {
            return DONE;
        }
    }

    
Increments the iterator's index by one and returns the character
at the new index.  If the resulting index is greater or equal
to getEndIndex(), the current index is reset to getEndIndex() and
a value of DONE is returned.

Returns:the character at the new position or DONE if the new
position is off the end of the text range.
/**
     * Increments the iterator's index by one and returns the character
     * at the new index.  If the resulting index is greater or equal
     * to getEndIndex(), the current index is reset to getEndIndex() and
     * a value of DONE is returned.
     * @return the character at the new position or DONE if the new
     * position is off the end of the text range.
     */
    public char next() {

        if (pos < chars.length-1) {
            pos++;
            return chars[pos];
        }
        else {
            pos = chars.length;
            return DONE;
        }
    }

    
Decrements the iterator's index by one and returns the character
at the new index. If the current index is getBeginIndex(), the index
remains at getBeginIndex() and a value of DONE is returned.

Returns:the character at the new position or DONE if the current
position is equal to getBeginIndex().
/**
     * Decrements the iterator's index by one and returns the character
     * at the new index. If the current index is getBeginIndex(), the index
     * remains at getBeginIndex() and a value of DONE is returned.
     * @return the character at the new position or DONE if the current
     * position is equal to getBeginIndex().
     */
    public char previous() {

        if (pos > 0) {
            pos--;
            return chars[pos];
        }
        else {
            pos = 0;
            return DONE;
        }
    }

    
Sets the position to the specified position in the text and returns that
character.

Params:
  • position – the position within the text.  Valid values range from
getBeginIndex() to getEndIndex().  An IllegalArgumentException is thrown
if an invalid value is supplied.
Returns:the character at the specified position or DONE if the specified position is equal to getEndIndex()
/**
     * Sets the position to the specified position in the text and returns that
     * character.
     * @param position the position within the text.  Valid values range from
     * getBeginIndex() to getEndIndex().  An IllegalArgumentException is thrown
     * if an invalid value is supplied.
     * @return the character at the specified position or DONE if the specified position is equal to getEndIndex()
     */
    public char setIndex(int position) {

        position -= begin;
        if (position < 0 || position > chars.length) {
            throw new IllegalArgumentException("Invalid index");
        }
        pos = position;
        return current();
    }

    
Returns the start index of the text.

Returns:the index at which the text begins.
/**
     * Returns the start index of the text.
     * @return the index at which the text begins.
     */
    public int getBeginIndex() {
        return begin;
    }

    
Returns the end index of the text.  This index is the index of the first
character following the end of the text.

Returns:the index after the last character in the text
/**
     * Returns the end index of the text.  This index is the index of the first
     * character following the end of the text.
     * @return the index after the last character in the text
     */
    public int getEndIndex() {
        return begin+chars.length;
    }

    
Returns the current index.

Returns:the current index.
/**
     * Returns the current index.
     * @return the current index.
     */
    public int getIndex() {
        return begin+pos;
    }

    
Create a copy of this iterator

Returns:A copy of this
/**
     * Create a copy of this iterator
     * @return A copy of this
     */
    public Object clone() {
        CharArrayIterator c = new CharArrayIterator(chars, begin);
        c.pos = this.pos;
        return c;
    }

    void reset(char[] chars) {
        reset(chars, 0);
    }

    void reset(char[] chars, int begin) {

        this.chars = chars;
        this.begin = begin;
        pos = 0;
    }
}