https://openjdk.java.net/ 
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package java.util;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.StreamCorruptedException;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;


The Vector class implements a growable array of objects. Like an array, it contains components that can be accessed using an integer index. However, the size of a Vector can grow or shrink as needed to accommodate adding and removing items after the Vector has been created. 
Each vector tries to optimize storage management by maintaining a capacity and a capacityIncrement. The capacity is always at least as large as the vector size; it is usually larger because as components are added to the vector, the vector's storage increases in chunks the size of capacityIncrement. An application can increase the capacity of a vector before inserting a large number of components; this reduces the amount of incremental reallocation. 
 The iterators returned by this class's iterator and listIterator methods are fail-fast: if the vector is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future. The Enumerations returned by the elements method are not fail-fast; if the
Vector is structurally modified at any time after the enumeration is
created then the results of enumerating are undefined.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators
should be used only to detect bugs.

As of the Java 2 platform v1.2, this class was retrofitted to implement the List interface, making it a member of the 
Java Collections Framework. Unlike the new collection implementations, Vector is synchronized. If a thread-safe implementation is not needed, it is recommended to use ArrayList in place of Vector. 
Author: Lee Boynton,  Jonathan Payne
Type parameters:
  • <E> – Type of component elements
See Also:
Since:  1.0
/**
 * The {@code Vector} class implements a growable array of
 * objects. Like an array, it contains components that can be
 * accessed using an integer index. However, the size of a
 * {@code Vector} can grow or shrink as needed to accommodate
 * adding and removing items after the {@code Vector} has been created.
 *
 * <p>Each vector tries to optimize storage management by maintaining a
 * {@code capacity} and a {@code capacityIncrement}. The
 * {@code capacity} is always at least as large as the vector
 * size; it is usually larger because as components are added to the
 * vector, the vector's storage increases in chunks the size of
 * {@code capacityIncrement}. An application can increase the
 * capacity of a vector before inserting a large number of
 * components; this reduces the amount of incremental reallocation.
 *
 * <p id="fail-fast">
 * The iterators returned by this class's {@link #iterator() iterator} and
 * {@link #listIterator(int) listIterator} methods are <em>fail-fast</em>:
 * if the vector is structurally modified at any time after the iterator is
 * created, in any way except through the iterator's own
 * {@link ListIterator#remove() remove} or
 * {@link ListIterator#add(Object) add} methods, the iterator will throw a
 * {@link ConcurrentModificationException}.  Thus, in the face of
 * concurrent modification, the iterator fails quickly and cleanly, rather
 * than risking arbitrary, non-deterministic behavior at an undetermined
 * time in the future.  The {@link Enumeration Enumerations} returned by
 * the {@link #elements() elements} method are <em>not</em> fail-fast; if the
 * Vector is structurally modified at any time after the enumeration is
 * created then the results of enumerating are undefined.
 *
 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
 * as it is, generally speaking, impossible to make any hard guarantees in the
 * presence of unsynchronized concurrent modification.  Fail-fast iterators
 * throw {@code ConcurrentModificationException} on a best-effort basis.
 * Therefore, it would be wrong to write a program that depended on this
 * exception for its correctness:  <i>the fail-fast behavior of iterators
 * should be used only to detect bugs.</i>
 *
 * <p>As of the Java 2 platform v1.2, this class was retrofitted to
 * implement the {@link List} interface, making it a member of the
 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
 * Java Collections Framework</a>.  Unlike the new collection
 * implementations, {@code Vector} is synchronized.  If a thread-safe
 * implementation is not needed, it is recommended to use {@link
 * ArrayList} in place of {@code Vector}.
 *
 * @param <E> Type of component elements
 *
 * @author  Lee Boynton
 * @author  Jonathan Payne
 * @see Collection
 * @see LinkedList
 * @since   1.0
 */
public class Vector<E>
    extends AbstractList<E>
    implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
    
The array buffer into which the components of the vector are
stored. The capacity of the vector is the length of this array buffer,
and is at least large enough to contain all the vector's elements.

Any array elements following the last element in the Vector are null.

@serial
/**
     * The array buffer into which the components of the vector are
     * stored. The capacity of the vector is the length of this array buffer,
     * and is at least large enough to contain all the vector's elements.
     *
     * <p>Any array elements following the last element in the Vector are null.
     *
     * @serial
     */
    protected Object[] elementData;

    
The number of valid components in this Vector object. Components elementData[0] through elementData[elementCount-1] are the actual items. 
@serial
/**
     * The number of valid components in this {@code Vector} object.
     * Components {@code elementData[0]} through
     * {@code elementData[elementCount-1]} are the actual items.
     *
     * @serial
     */
    protected int elementCount;

    
The amount by which the capacity of the vector is automatically
incremented when its size becomes greater than its capacity.  If
the capacity increment is less than or equal to zero, the capacity
of the vector is doubled each time it needs to grow.

@serial
/**
     * The amount by which the capacity of the vector is automatically
     * incremented when its size becomes greater than its capacity.  If
     * the capacity increment is less than or equal to zero, the capacity
     * of the vector is doubled each time it needs to grow.
     *
     * @serial
     */
    protected int capacityIncrement;

    
use serialVersionUID from JDK 1.0.2 for interoperability 
/** use serialVersionUID from JDK 1.0.2 for interoperability */
    private static final long serialVersionUID = -2767605614048989439L;

    
Constructs an empty vector with the specified initial capacity and
capacity increment.

Params:
  • initialCapacity –     the initial capacity of the vector
  • capacityIncrement –   the amount by which the capacity is
                             increased when the vector overflows
Throws:
/**
     * Constructs an empty vector with the specified initial capacity and
     * capacity increment.
     *
     * @param   initialCapacity     the initial capacity of the vector
     * @param   capacityIncrement   the amount by which the capacity is
     *                              increased when the vector overflows
     * @throws IllegalArgumentException if the specified initial capacity
     *         is negative
     */
    public Vector(int initialCapacity, int capacityIncrement) {
        super();
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Capacity: "+
                                               initialCapacity);
        this.elementData = new Object[initialCapacity];
        this.capacityIncrement = capacityIncrement;
    }

    
Constructs an empty vector with the specified initial capacity and
with its capacity increment equal to zero.

Params:
  • initialCapacity –   the initial capacity of the vector
Throws:
/**
     * Constructs an empty vector with the specified initial capacity and
     * with its capacity increment equal to zero.
     *
     * @param   initialCapacity   the initial capacity of the vector
     * @throws IllegalArgumentException if the specified initial capacity
     *         is negative
     */
    public Vector(int initialCapacity) {
        this(initialCapacity, 0);
    }

    
Constructs an empty vector so that its internal data array has size 10 and its standard capacity increment is zero. 
/**
     * Constructs an empty vector so that its internal data array
     * has size {@code 10} and its standard capacity increment is
     * zero.
     */
    public Vector() {
        this(10);
    }

    
Constructs a vector containing the elements of the specified
collection, in the order they are returned by the collection's
iterator.

Params:
  • c – the collection whose elements are to be placed into this
      vector
Throws:
Since:  1.2
/**
     * Constructs a vector containing the elements of the specified
     * collection, in the order they are returned by the collection's
     * iterator.
     *
     * @param c the collection whose elements are to be placed into this
     *       vector
     * @throws NullPointerException if the specified collection is null
     * @since   1.2
     */
    public Vector(Collection<? extends E> c) {
        Object[] a = c.toArray();
        elementCount = a.length;
        if (c.getClass() == ArrayList.class) {
            elementData = a;
        } else {
            elementData = Arrays.copyOf(a, elementCount, Object[].class);
        }
    }

    
Copies the components of this vector into the specified array. The item at index k in this vector is copied into component k of anArray. 
Params:
  • anArray – the array into which the components get copied
Throws:
See Also:
/**
     * Copies the components of this vector into the specified array.
     * The item at index {@code k} in this vector is copied into
     * component {@code k} of {@code anArray}.
     *
     * @param  anArray the array into which the components get copied
     * @throws NullPointerException if the given array is null
     * @throws IndexOutOfBoundsException if the specified array is not
     *         large enough to hold all the components of this vector
     * @throws ArrayStoreException if a component of this vector is not of
     *         a runtime type that can be stored in the specified array
     * @see #toArray(Object[])
     */
    public synchronized void copyInto(Object[] anArray) {
        System.arraycopy(elementData, 0, anArray, 0, elementCount);
    }

    
Trims the capacity of this vector to be the vector's current size. If the capacity of this vector is larger than its current size, then the capacity is changed to equal the size by replacing its internal data array, kept in the field elementData, with a smaller one. An application can use this operation to minimize the storage of a vector. 
/**
     * Trims the capacity of this vector to be the vector's current
     * size. If the capacity of this vector is larger than its current
     * size, then the capacity is changed to equal the size by replacing
     * its internal data array, kept in the field {@code elementData},
     * with a smaller one. An application can use this operation to
     * minimize the storage of a vector.
     */
    public synchronized void trimToSize() {
        modCount++;
        int oldCapacity = elementData.length;
        if (elementCount < oldCapacity) {
            elementData = Arrays.copyOf(elementData, elementCount);
        }
    }

    
Increases the capacity of this vector, if necessary, to ensure
that it can hold at least the number of components specified by
the minimum capacity argument.

If the current capacity of this vector is less than minCapacity, then its capacity is increased by replacing its internal data array, kept in the field elementData, with a larger one. The size of the new data array will be the old size plus capacityIncrement, unless the value of capacityIncrement is less than or equal to zero, in which case the new capacity will be twice the old capacity; but if this new size is still smaller than minCapacity, then the new capacity will be minCapacity. 
Params:
  • minCapacity – the desired minimum capacity
/**
     * Increases the capacity of this vector, if necessary, to ensure
     * that it can hold at least the number of components specified by
     * the minimum capacity argument.
     *
     * <p>If the current capacity of this vector is less than
     * {@code minCapacity}, then its capacity is increased by replacing its
     * internal data array, kept in the field {@code elementData}, with a
     * larger one.  The size of the new data array will be the old size plus
     * {@code capacityIncrement}, unless the value of
     * {@code capacityIncrement} is less than or equal to zero, in which case
     * the new capacity will be twice the old capacity; but if this new size
     * is still smaller than {@code minCapacity}, then the new capacity will
     * be {@code minCapacity}.
     *
     * @param minCapacity the desired minimum capacity
     */
    public synchronized void ensureCapacity(int minCapacity) {
        if (minCapacity > 0) {
            modCount++;
            if (minCapacity > elementData.length)
                grow(minCapacity);
        }
    }

    
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

/**
     * 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;

    
Increases the capacity to ensure that it can hold at least the
number of elements specified by the minimum capacity argument.

Params:
  • minCapacity – the desired minimum capacity
Throws:
/**
     * Increases the capacity to ensure that it can hold at least the
     * number of elements specified by the minimum capacity argument.
     *
     * @param minCapacity the desired minimum capacity
     * @throws OutOfMemoryError if minCapacity is less than zero
     */
    private Object[] grow(int minCapacity) {
        return elementData = Arrays.copyOf(elementData,
                                           newCapacity(minCapacity));
    }

    private Object[] grow() {
        return grow(elementCount + 1);
    }

    
Returns a capacity at least as large as the given minimum capacity.
Will not return a capacity greater than MAX_ARRAY_SIZE unless
the given minimum capacity is greater than MAX_ARRAY_SIZE.

Params:
  • minCapacity – the desired minimum capacity
Throws:
/**
     * Returns a capacity at least as large as the given minimum capacity.
     * Will not return a capacity greater than MAX_ARRAY_SIZE unless
     * the given minimum capacity is greater than MAX_ARRAY_SIZE.
     *
     * @param minCapacity the desired minimum capacity
     * @throws OutOfMemoryError if minCapacity is less than zero
     */
    private int newCapacity(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = elementData.length;
        int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
                                         capacityIncrement : oldCapacity);
        if (newCapacity - minCapacity <= 0) {
            if (minCapacity < 0) // overflow
                throw new OutOfMemoryError();
            return minCapacity;
        }
        return (newCapacity - MAX_ARRAY_SIZE <= 0)
            ? newCapacity
            : hugeCapacity(minCapacity);
    }

    private static int hugeCapacity(int minCapacity) {
        if (minCapacity < 0) // overflow
            throw new OutOfMemoryError();
        return (minCapacity > MAX_ARRAY_SIZE) ?
            Integer.MAX_VALUE :
            MAX_ARRAY_SIZE;
    }

    
Sets the size of this vector. If the new size is greater than the current size, new null items are added to the end of the vector. If the new size is less than the current size, all components at index newSize and greater are discarded. 
Params:
  • newSize –   the new size of this vector
Throws:
/**
     * Sets the size of this vector. If the new size is greater than the
     * current size, new {@code null} items are added to the end of
     * the vector. If the new size is less than the current size, all
     * components at index {@code newSize} and greater are discarded.
     *
     * @param  newSize   the new size of this vector
     * @throws ArrayIndexOutOfBoundsException if the new size is negative
     */
    public synchronized void setSize(int newSize) {
        modCount++;
        if (newSize > elementData.length)
            grow(newSize);
        final Object[] es = elementData;
        for (int to = elementCount, i = newSize; i < to; i++)
            es[i] = null;
        elementCount = newSize;
    }

    
Returns the current capacity of this vector.

Returns: the current capacity (the length of its internal data array, kept in the field elementData of this vector)
/**
     * Returns the current capacity of this vector.
     *
     * @return  the current capacity (the length of its internal
     *          data array, kept in the field {@code elementData}
     *          of this vector)
     */
    public synchronized int capacity() {
        return elementData.length;
    }

    
Returns the number of components in this vector.

Returns: the number of components in this vector
/**
     * Returns the number of components in this vector.
     *
     * @return  the number of components in this vector
     */
    public synchronized int size() {
        return elementCount;
    }

    
Tests if this vector has no components.

Returns: true if and only if this vector has no components, that is, its size is zero; false otherwise.
/**
     * Tests if this vector has no components.
     *
     * @return  {@code true} if and only if this vector has
     *          no components, that is, its size is zero;
     *          {@code false} otherwise.
     */
    public synchronized boolean isEmpty() {
        return elementCount == 0;
    }

    
Returns an enumeration of the components of this vector. The returned Enumeration object will generate all items in this vector. The first item generated is the item at index 0, then the item at index 1, and so on. If the vector is structurally modified while enumerating over the elements then the results of enumerating are undefined. 
See Also:
Returns: an enumeration of the components of this vector
/**
     * Returns an enumeration of the components of this vector. The
     * returned {@code Enumeration} object will generate all items in
     * this vector. The first item generated is the item at index {@code 0},
     * then the item at index {@code 1}, and so on. If the vector is
     * structurally modified while enumerating over the elements then the
     * results of enumerating are undefined.
     *
     * @return  an enumeration of the components of this vector
     * @see     Iterator
     */
    public Enumeration<E> elements() {
        return new Enumeration<E>() {
            int count = 0;

            public boolean hasMoreElements() {
                return count < elementCount;
            }

            public E nextElement() {
                synchronized (Vector.this) {
                    if (count < elementCount) {
                        return elementData(count++);
                    }
                }
                throw new NoSuchElementException("Vector Enumeration");
            }
        };
    }

    
Returns true if this vector contains the specified element. More formally, returns true if and only if this vector contains at least one element e such that Objects.equals(o, e). 
Params:
  • o – element whose presence in this vector is to be tested
Returns:true if this vector contains the specified element
/**
     * Returns {@code true} if this vector contains the specified element.
     * More formally, returns {@code true} if and only if this vector
     * contains at least one element {@code e} such that
     * {@code Objects.equals(o, e)}.
     *
     * @param o element whose presence in this vector is to be tested
     * @return {@code true} if this vector contains the specified element
     */
    public boolean contains(Object o) {
        return indexOf(o, 0) >= 0;
    }

    
Returns the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element. More formally, returns the lowest index i such that Objects.equals(o, get(i)), or -1 if there is no such index. 
Params:
  • o – element to search for
Returns:the index of the first occurrence of the specified element in
        this vector, or -1 if this vector does not contain the element
/**
     * Returns the index of the first occurrence of the specified element
     * in this vector, or -1 if this vector does not contain the element.
     * More formally, returns the lowest index {@code i} such that
     * {@code Objects.equals(o, get(i))},
     * or -1 if there is no such index.
     *
     * @param o element to search for
     * @return the index of the first occurrence of the specified element in
     *         this vector, or -1 if this vector does not contain the element
     */
    public int indexOf(Object o) {
        return indexOf(o, 0);
    }

    
Returns the index of the first occurrence of the specified element in this vector, searching forwards from index, or returns -1 if the element is not found. More formally, returns the lowest index i such that (i >= index && Objects.equals(o, get(i))), or -1 if there is no such index. 
Params:
  • o – element to search for
  • index – index to start searching from
Throws:
See Also:
Returns:the index of the first occurrence of the element in this vector at position index or later in the vector; -1 if the element is not found.
/**
     * Returns the index of the first occurrence of the specified element in
     * this vector, searching forwards from {@code index}, or returns -1 if
     * the element is not found.
     * More formally, returns the lowest index {@code i} such that
     * {@code (i >= index && Objects.equals(o, get(i)))},
     * or -1 if there is no such index.
     *
     * @param o element to search for
     * @param index index to start searching from
     * @return the index of the first occurrence of the element in
     *         this vector at position {@code index} or later in the vector;
     *         {@code -1} if the element is not found.
     * @throws IndexOutOfBoundsException if the specified index is negative
     * @see     Object#equals(Object)
     */
    public synchronized int indexOf(Object o, int index) {
        if (o == null) {
            for (int i = index ; i < elementCount ; i++)
                if (elementData[i]==null)
                    return i;
        } else {
            for (int i = index ; i < elementCount ; i++)
                if (o.equals(elementData[i]))
                    return i;
        }
        return -1;
    }

    
Returns the index of the last occurrence of the specified element in this vector, or -1 if this vector does not contain the element. More formally, returns the highest index i such that Objects.equals(o, get(i)), or -1 if there is no such index. 
Params:
  • o – element to search for
Returns:the index of the last occurrence of the specified element in
        this vector, or -1 if this vector does not contain the element
/**
     * Returns the index of the last occurrence of the specified element
     * in this vector, or -1 if this vector does not contain the element.
     * More formally, returns the highest index {@code i} such that
     * {@code Objects.equals(o, get(i))},
     * or -1 if there is no such index.
     *
     * @param o element to search for
     * @return the index of the last occurrence of the specified element in
     *         this vector, or -1 if this vector does not contain the element
     */
    public synchronized int lastIndexOf(Object o) {
        return lastIndexOf(o, elementCount-1);
    }

    
Returns the index of the last occurrence of the specified element in this vector, searching backwards from index, or returns -1 if the element is not found. More formally, returns the highest index i such that (i <= index && Objects.equals(o, get(i))), or -1 if there is no such index. 
Params:
  • o – element to search for
  • index – index to start searching backwards from
Throws:
Returns:the index of the last occurrence of the element at position less than or equal to index in this vector; -1 if the element is not found.
/**
     * Returns the index of the last occurrence of the specified element in
     * this vector, searching backwards from {@code index}, or returns -1 if
     * the element is not found.
     * More formally, returns the highest index {@code i} such that
     * {@code (i <= index && Objects.equals(o, get(i)))},
     * or -1 if there is no such index.
     *
     * @param o element to search for
     * @param index index to start searching backwards from
     * @return the index of the last occurrence of the element at position
     *         less than or equal to {@code index} in this vector;
     *         -1 if the element is not found.
     * @throws IndexOutOfBoundsException if the specified index is greater
     *         than or equal to the current size of this vector
     */
    public synchronized int lastIndexOf(Object o, int index) {
        if (index >= elementCount)
            throw new IndexOutOfBoundsException(index + " >= "+ elementCount);

        if (o == null) {
            for (int i = index; i >= 0; i--)
                if (elementData[i]==null)
                    return i;
        } else {
            for (int i = index; i >= 0; i--)
                if (o.equals(elementData[i]))
                    return i;
        }
        return -1;
    }

    
Returns the component at the specified index.

This method is identical in functionality to the get(int) method (which is part of the List interface). 
Params:
  • index –   an index into this vector
Throws:
Returns:    the component at the specified index
/**
     * Returns the component at the specified index.
     *
     * <p>This method is identical in functionality to the {@link #get(int)}
     * method (which is part of the {@link List} interface).
     *
     * @param      index   an index into this vector
     * @return     the component at the specified index
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index >= size()})
     */
    public synchronized E elementAt(int index) {
        if (index >= elementCount) {
            throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
        }

        return elementData(index);
    }

    
Returns the first component (the item at index 0) of this vector. 
Throws:
Returns:    the first component of this vector
/**
     * Returns the first component (the item at index {@code 0}) of
     * this vector.
     *
     * @return     the first component of this vector
     * @throws NoSuchElementException if this vector has no components
     */
    public synchronized E firstElement() {
        if (elementCount == 0) {
            throw new NoSuchElementException();
        }
        return elementData(0);
    }

    
Returns the last component of the vector.

Throws:
Returns: the last component of the vector, i.e., the component at index size() - 1
/**
     * Returns the last component of the vector.
     *
     * @return  the last component of the vector, i.e., the component at index
     *          {@code size() - 1}
     * @throws NoSuchElementException if this vector is empty
     */
    public synchronized E lastElement() {
        if (elementCount == 0) {
            throw new NoSuchElementException();
        }
        return elementData(elementCount - 1);
    }

    
Sets the component at the specified index of this vector to be the specified object. The previous component at that position is discarded. 
The index must be a value greater than or equal to 0 and less than the current size of the vector. 
This method is identical in functionality to the set(int, E) method (which is part of the List interface). Note that the set method reverses the order of the parameters, to more closely match array usage. Note also that the set method returns the old value that was stored at the specified position. 
Params:
  • obj –     what the component is to be set to
  • index –   the specified index
Throws:
/**
     * Sets the component at the specified {@code index} of this
     * vector to be the specified object. The previous component at that
     * position is discarded.
     *
     * <p>The index must be a value greater than or equal to {@code 0}
     * and less than the current size of the vector.
     *
     * <p>This method is identical in functionality to the
     * {@link #set(int, Object) set(int, E)}
     * method (which is part of the {@link List} interface). Note that the
     * {@code set} method reverses the order of the parameters, to more closely
     * match array usage.  Note also that the {@code set} method returns the
     * old value that was stored at the specified position.
     *
     * @param      obj     what the component is to be set to
     * @param      index   the specified index
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index >= size()})
     */
    public synchronized void setElementAt(E obj, int index) {
        if (index >= elementCount) {
            throw new ArrayIndexOutOfBoundsException(index + " >= " +
                                                     elementCount);
        }
        elementData[index] = obj;
    }

    
Deletes the component at the specified index. Each component in this vector with an index greater or equal to the specified index is shifted downward to have an index one smaller than the value it had previously. The size of this vector is decreased by 1. 
The index must be a value greater than or equal to 0 and less than the current size of the vector. 
This method is identical in functionality to the remove(int) method (which is part of the List interface). Note that the remove method returns the old value that was stored at the specified position. 
Params:
  • index –   the index of the object to remove
Throws:
/**
     * Deletes the component at the specified index. Each component in
     * this vector with an index greater or equal to the specified
     * {@code index} is shifted downward to have an index one
     * smaller than the value it had previously. The size of this vector
     * is decreased by {@code 1}.
     *
     * <p>The index must be a value greater than or equal to {@code 0}
     * and less than the current size of the vector.
     *
     * <p>This method is identical in functionality to the {@link #remove(int)}
     * method (which is part of the {@link List} interface).  Note that the
     * {@code remove} method returns the old value that was stored at the
     * specified position.
     *
     * @param      index   the index of the object to remove
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index >= size()})
     */
    public synchronized void removeElementAt(int index) {
        if (index >= elementCount) {
            throw new ArrayIndexOutOfBoundsException(index + " >= " +
                                                     elementCount);
        }
        else if (index < 0) {
            throw new ArrayIndexOutOfBoundsException(index);
        }
        int j = elementCount - index - 1;
        if (j > 0) {
            System.arraycopy(elementData, index + 1, elementData, index, j);
        }
        modCount++;
        elementCount--;
        elementData[elementCount] = null; /* to let gc do its work */
    }

    
Inserts the specified object as a component in this vector at the specified index. Each component in this vector with an index greater or equal to the specified index is shifted upward to have an index one greater than the value it had previously. 
The index must be a value greater than or equal to 0 and less than or equal to the current size of the vector. (If the index is equal to the current size of the vector, the new element is appended to the Vector.) 
This method is identical in functionality to the add(int, E) method (which is part of the List interface). Note that the add method reverses the order of the parameters, to more closely match array usage. 
Params:
  • obj –     the component to insert
  • index –   where to insert the new component
Throws:
/**
     * Inserts the specified object as a component in this vector at the
     * specified {@code index}. Each component in this vector with
     * an index greater or equal to the specified {@code index} is
     * shifted upward to have an index one greater than the value it had
     * previously.
     *
     * <p>The index must be a value greater than or equal to {@code 0}
     * and less than or equal to the current size of the vector. (If the
     * index is equal to the current size of the vector, the new element
     * is appended to the Vector.)
     *
     * <p>This method is identical in functionality to the
     * {@link #add(int, Object) add(int, E)}
     * method (which is part of the {@link List} interface).  Note that the
     * {@code add} method reverses the order of the parameters, to more closely
     * match array usage.
     *
     * @param      obj     the component to insert
     * @param      index   where to insert the new component
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index > size()})
     */
    public synchronized void insertElementAt(E obj, int index) {
        if (index > elementCount) {
            throw new ArrayIndexOutOfBoundsException(index
                                                     + " > " + elementCount);
        }
        modCount++;
        final int s = elementCount;
        Object[] elementData = this.elementData;
        if (s == elementData.length)
            elementData = grow();
        System.arraycopy(elementData, index,
                         elementData, index + 1,
                         s - index);
        elementData[index] = obj;
        elementCount = s + 1;
    }

    
Adds the specified component to the end of this vector,
increasing its size by one. The capacity of this vector is
increased if its size becomes greater than its capacity.

This method is identical in functionality to the add(E) method (which is part of the List interface). 
Params:
  • obj –   the component to be added
/**
     * Adds the specified component to the end of this vector,
     * increasing its size by one. The capacity of this vector is
     * increased if its size becomes greater than its capacity.
     *
     * <p>This method is identical in functionality to the
     * {@link #add(Object) add(E)}
     * method (which is part of the {@link List} interface).
     *
     * @param   obj   the component to be added
     */
    public synchronized void addElement(E obj) {
        modCount++;
        add(obj, elementData, elementCount);
    }

    
Removes the first (lowest-indexed) occurrence of the argument
from this vector. If the object is found in this vector, each
component in the vector with an index greater or equal to the
object's index is shifted downward to have an index one smaller
than the value it had previously.

This method is identical in functionality to the remove(Object) method (which is part of the List interface). 
Params:
  • obj –   the component to be removed
Returns: true if the argument was a component of this vector; false otherwise.
/**
     * Removes the first (lowest-indexed) occurrence of the argument
     * from this vector. If the object is found in this vector, each
     * component in the vector with an index greater or equal to the
     * object's index is shifted downward to have an index one smaller
     * than the value it had previously.
     *
     * <p>This method is identical in functionality to the
     * {@link #remove(Object)} method (which is part of the
     * {@link List} interface).
     *
     * @param   obj   the component to be removed
     * @return  {@code true} if the argument was a component of this
     *          vector; {@code false} otherwise.
     */
    public synchronized boolean removeElement(Object obj) {
        modCount++;
        int i = indexOf(obj);
        if (i >= 0) {
            removeElementAt(i);
            return true;
        }
        return false;
    }

    
Removes all components from this vector and sets its size to zero.

This method is identical in functionality to the clear method (which is part of the List interface). 
/**
     * Removes all components from this vector and sets its size to zero.
     *
     * <p>This method is identical in functionality to the {@link #clear}
     * method (which is part of the {@link List} interface).
     */
    public synchronized void removeAllElements() {
        final Object[] es = elementData;
        for (int to = elementCount, i = elementCount = 0; i < to; i++)
            es[i] = null;
        modCount++;
    }

    
Returns a clone of this vector. The copy will contain a reference to a clone of the internal data array, not a reference to the original internal data array of this Vector object. 
Returns: a clone of this vector
/**
     * Returns a clone of this vector. The copy will contain a
     * reference to a clone of the internal data array, not a reference
     * to the original internal data array of this {@code Vector} object.
     *
     * @return  a clone of this vector
     */
    public synchronized Object clone() {
        try {
            @SuppressWarnings("unchecked")
            Vector<E> v = (Vector<E>) super.clone();
            v.elementData = Arrays.copyOf(elementData, elementCount);
            v.modCount = 0;
            return v;
        } catch (CloneNotSupportedException e) {
            // this shouldn't happen, since we are Cloneable
            throw new InternalError(e);
        }
    }

    
Returns an array containing all of the elements in this Vector
in the correct order.

Since:1.2
/**
     * Returns an array containing all of the elements in this Vector
     * in the correct order.
     *
     * @since 1.2
     */
    public synchronized Object[] toArray() {
        return Arrays.copyOf(elementData, elementCount);
    }

    
Returns an array containing all of the elements in this Vector in the
correct order; the runtime type of the returned array is that of the
specified array.  If the Vector fits in the specified array, it is
returned therein.  Otherwise, a new array is allocated with the runtime
type of the specified array and the size of this Vector.

If the Vector fits in the specified array with room to spare
(i.e., the array has more elements than the Vector),
the element in the array immediately following the end of the
Vector is set to null.  (This is useful in determining the length
of the Vector only if the caller knows that the Vector
does not contain any null elements.)

Params:
  • a – the array into which the elements of the Vector are to
         be stored, if it is big enough; otherwise, a new array of the
         same runtime type is allocated for this purpose.
Type parameters:
  • <T> – type of array elements. The same type as <E> or a supertype of <E>.
Throws:
Returns:an array containing the elements of the Vector
Since:1.2
/**
     * Returns an array containing all of the elements in this Vector in the
     * correct order; the runtime type of the returned array is that of the
     * specified array.  If the Vector fits in the specified array, it is
     * returned therein.  Otherwise, a new array is allocated with the runtime
     * type of the specified array and the size of this Vector.
     *
     * <p>If the Vector fits in the specified array with room to spare
     * (i.e., the array has more elements than the Vector),
     * the element in the array immediately following the end of the
     * Vector is set to null.  (This is useful in determining the length
     * of the Vector <em>only</em> if the caller knows that the Vector
     * does not contain any null elements.)
     *
     * @param <T> type of array elements. The same type as {@code <E>} or a
     * supertype of {@code <E>}.
     * @param a the array into which the elements of the Vector are to
     *          be stored, if it is big enough; otherwise, a new array of the
     *          same runtime type is allocated for this purpose.
     * @return an array containing the elements of the Vector
     * @throws ArrayStoreException if the runtime type of a, {@code <T>}, is not
     * a supertype of the runtime type, {@code <E>}, of every element in this
     * Vector
     * @throws NullPointerException if the given array is null
     * @since 1.2
     */
    @SuppressWarnings("unchecked")
    public synchronized <T> T[] toArray(T[] a) {
        if (a.length < elementCount)
            return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());

        System.arraycopy(elementData, 0, a, 0, elementCount);

        if (a.length > elementCount)
            a[elementCount] = null;

        return a;
    }

    // Positional Access Operations

    @SuppressWarnings("unchecked")
    E elementData(int index) {
        return (E) elementData[index];
    }

    @SuppressWarnings("unchecked")
    static <E> E elementAt(Object[] es, int index) {
        return (E) es[index];
    }

    
Returns the element at the specified position in this Vector.

Params:
  • index – index of the element to return
Throws:
Returns:object at the specified index
Since:1.2
/**
     * Returns the element at the specified position in this Vector.
     *
     * @param index index of the element to return
     * @return object at the specified index
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *            ({@code index < 0 || index >= size()})
     * @since 1.2
     */
    public synchronized E get(int index) {
        if (index >= elementCount)
            throw new ArrayIndexOutOfBoundsException(index);

        return elementData(index);
    }

    
Replaces the element at the specified position in this Vector with the
specified element.

Params:
  • index – index of the element to replace
  • element – element to be stored at the specified position
Throws:
Returns:the element previously at the specified position
Since:1.2
/**
     * Replaces the element at the specified position in this Vector with the
     * specified element.
     *
     * @param index index of the element to replace
     * @param element element to be stored at the specified position
     * @return the element previously at the specified position
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index >= size()})
     * @since 1.2
     */
    public synchronized E set(int index, E element) {
        if (index >= elementCount)
            throw new ArrayIndexOutOfBoundsException(index);

        E oldValue = elementData(index);
        elementData[index] = element;
        return oldValue;
    }

    
This helper method split out from add(E) to keep method
bytecode size under 35 (the -XX:MaxInlineSize default value),
which helps when add(E) is called in a C1-compiled loop.

/**
     * This helper method split out from add(E) to keep method
     * bytecode size under 35 (the -XX:MaxInlineSize default value),
     * which helps when add(E) is called in a C1-compiled loop.
     */
    private void add(E e, Object[] elementData, int s) {
        if (s == elementData.length)
            elementData = grow();
        elementData[s] = e;
        elementCount = s + 1;
    }

    
Appends the specified element to the end of this Vector.

Params:
  • e – element to be appended to this Vector
Returns:true (as specified by Collection.add)
Since:1.2
/**
     * Appends the specified element to the end of this Vector.
     *
     * @param e element to be appended to this Vector
     * @return {@code true} (as specified by {@link Collection#add})
     * @since 1.2
     */
    public synchronized boolean add(E e) {
        modCount++;
        add(e, elementData, elementCount);
        return true;
    }

    
Removes the first occurrence of the specified element in this Vector If the Vector does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that Objects.equals(o, get(i)) (if such an element exists). 
Params:
  • o – element to be removed from this Vector, if present
Returns:true if the Vector contained the specified element
Since:1.2
/**
     * Removes the first occurrence of the specified element in this Vector
     * If the Vector does not contain the element, it is unchanged.  More
     * formally, removes the element with the lowest index i such that
     * {@code Objects.equals(o, get(i))} (if such
     * an element exists).
     *
     * @param o element to be removed from this Vector, if present
     * @return true if the Vector contained the specified element
     * @since 1.2
     */
    public boolean remove(Object o) {
        return removeElement(o);
    }

    
Inserts the specified element at the specified position in this Vector.
Shifts the element currently at that position (if any) and any
subsequent elements to the right (adds one to their indices).

Params:
  • index – index at which the specified element is to be inserted
  • element – element to be inserted
Throws:
Since:1.2
/**
     * Inserts the specified element at the specified position in this Vector.
     * Shifts the element currently at that position (if any) and any
     * subsequent elements to the right (adds one to their indices).
     *
     * @param index index at which the specified element is to be inserted
     * @param element element to be inserted
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index > size()})
     * @since 1.2
     */
    public void add(int index, E element) {
        insertElementAt(element, index);
    }

    
Removes the element at the specified position in this Vector.
Shifts any subsequent elements to the left (subtracts one from their
indices).  Returns the element that was removed from the Vector.

Params:
  • index – the index of the element to be removed
Throws:
Returns:element that was removed
Since:1.2
/**
     * Removes the element at the specified position in this Vector.
     * Shifts any subsequent elements to the left (subtracts one from their
     * indices).  Returns the element that was removed from the Vector.
     *
     * @param index the index of the element to be removed
     * @return element that was removed
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index >= size()})
     * @since 1.2
     */
    public synchronized E remove(int index) {
        modCount++;
        if (index >= elementCount)
            throw new ArrayIndexOutOfBoundsException(index);
        E oldValue = elementData(index);

        int numMoved = elementCount - index - 1;
        if (numMoved > 0)
            System.arraycopy(elementData, index+1, elementData, index,
                             numMoved);
        elementData[--elementCount] = null; // Let gc do its work

        return oldValue;
    }

    
Removes all of the elements from this Vector.  The Vector will
be empty after this call returns (unless it throws an exception).

Since:1.2
/**
     * Removes all of the elements from this Vector.  The Vector will
     * be empty after this call returns (unless it throws an exception).
     *
     * @since 1.2
     */
    public void clear() {
        removeAllElements();
    }

    // Bulk Operations

    
Returns true if this Vector contains all of the elements in the
specified Collection.

Params:
  • c – a collection whose elements will be tested for containment
         in this Vector
Throws:
Returns:true if this Vector contains all of the elements in the
        specified collection
/**
     * Returns true if this Vector contains all of the elements in the
     * specified Collection.
     *
     * @param   c a collection whose elements will be tested for containment
     *          in this Vector
     * @return true if this Vector contains all of the elements in the
     *         specified collection
     * @throws NullPointerException if the specified collection is null
     */
    public synchronized boolean containsAll(Collection<?> c) {
        return super.containsAll(c);
    }

    
Appends all of the elements in the specified Collection to the end of
this Vector, in the order that they are returned by the specified
Collection's Iterator.  The behavior of this operation is undefined if
the specified Collection is modified while the operation is in progress.
(This implies that the behavior of this call is undefined if the
specified Collection is this Vector, and this Vector is nonempty.)

Params:
  • c – elements to be inserted into this Vector
Throws:
Returns:true if this Vector changed as a result of the call
Since:1.2
/**
     * Appends all of the elements in the specified Collection to the end of
     * this Vector, in the order that they are returned by the specified
     * Collection's Iterator.  The behavior of this operation is undefined if
     * the specified Collection is modified while the operation is in progress.
     * (This implies that the behavior of this call is undefined if the
     * specified Collection is this Vector, and this Vector is nonempty.)
     *
     * @param c elements to be inserted into this Vector
     * @return {@code true} if this Vector changed as a result of the call
     * @throws NullPointerException if the specified collection is null
     * @since 1.2
     */
    public boolean addAll(Collection<? extends E> c) {
        Object[] a = c.toArray();
        modCount++;
        int numNew = a.length;
        if (numNew == 0)
            return false;
        synchronized (this) {
            Object[] elementData = this.elementData;
            final int s = elementCount;
            if (numNew > elementData.length - s)
                elementData = grow(s + numNew);
            System.arraycopy(a, 0, elementData, s, numNew);
            elementCount = s + numNew;
            return true;
        }
    }

    
Removes from this Vector all of its elements that are contained in the
specified Collection.

Params:
  • c – a collection of elements to be removed from the Vector
Throws:
  • ClassCastException – if the types of one or more elements
        in this vector are incompatible with the specified
        collection
(optional)
  • NullPointerException – if this vector contains one or more null
        elements and the specified collection does not support null
        elements
(optional),
        or if the specified collection is null
Returns:true if this Vector changed as a result of the call
Since:1.2
/**
     * Removes from this Vector all of its elements that are contained in the
     * specified Collection.
     *
     * @param c a collection of elements to be removed from the Vector
     * @return true if this Vector changed as a result of the call
     * @throws ClassCastException if the types of one or more elements
     *         in this vector are incompatible with the specified
     *         collection
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if this vector contains one or more null
     *         elements and the specified collection does not support null
     *         elements
     * (<a href="Collection.html#optional-restrictions">optional</a>),
     *         or if the specified collection is null
     * @since 1.2
     */
    public boolean removeAll(Collection<?> c) {
        Objects.requireNonNull(c);
        return bulkRemove(e -> c.contains(e));
    }

    
Retains only the elements in this Vector that are contained in the
specified Collection.  In other words, removes from this Vector all
of its elements that are not contained in the specified Collection.

Params:
  • c – a collection of elements to be retained in this Vector
         (all other elements are removed)
Throws:
  • ClassCastException – if the types of one or more elements
        in this vector are incompatible with the specified
        collection
(optional)
  • NullPointerException – if this vector contains one or more null
        elements and the specified collection does not support null
        elements
        (optional),
        or if the specified collection is null
Returns:true if this Vector changed as a result of the call
Since:1.2
/**
     * Retains only the elements in this Vector that are contained in the
     * specified Collection.  In other words, removes from this Vector all
     * of its elements that are not contained in the specified Collection.
     *
     * @param c a collection of elements to be retained in this Vector
     *          (all other elements are removed)
     * @return true if this Vector changed as a result of the call
     * @throws ClassCastException if the types of one or more elements
     *         in this vector are incompatible with the specified
     *         collection
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if this vector contains one or more null
     *         elements and the specified collection does not support null
     *         elements
     *         (<a href="Collection.html#optional-restrictions">optional</a>),
     *         or if the specified collection is null
     * @since 1.2
     */
    public boolean retainAll(Collection<?> c) {
        Objects.requireNonNull(c);
        return bulkRemove(e -> !c.contains(e));
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
/**
     * @throws NullPointerException {@inheritDoc}
     */
    @Override
    public boolean removeIf(Predicate<? super E> filter) {
        Objects.requireNonNull(filter);
        return bulkRemove(filter);
    }

    // A tiny bit set implementation

    private static long[] nBits(int n) {
        return new long[((n - 1) >> 6) + 1];
    }
    private static void setBit(long[] bits, int i) {
        bits[i >> 6] |= 1L << i;
    }
    private static boolean isClear(long[] bits, int i) {
        return (bits[i >> 6] & (1L << i)) == 0;
    }

    private synchronized boolean bulkRemove(Predicate<? super E> filter) {
        int expectedModCount = modCount;
        final Object[] es = elementData;
        final int end = elementCount;
        int i;
        // Optimize for initial run of survivors
        for (i = 0; i < end && !filter.test(elementAt(es, i)); i++)
            ;
        // Tolerate predicates that reentrantly access the collection for
        // read (but writers still get CME), so traverse once to find
        // elements to delete, a second pass to physically expunge.
        if (i < end) {
            final int beg = i;
            final long[] deathRow = nBits(end - beg);
            deathRow[0] = 1L;   // set bit 0
            for (i = beg + 1; i < end; i++)
                if (filter.test(elementAt(es, i)))
                    setBit(deathRow, i - beg);
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
            modCount++;
            int w = beg;
            for (i = beg; i < end; i++)
                if (isClear(deathRow, i - beg))
                    es[w++] = es[i];
            for (i = elementCount = w; i < end; i++)
                es[i] = null;
            return true;
        } else {
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
            return false;
        }
    }

    
Inserts all of the elements in the specified Collection into this
Vector at the specified position.  Shifts the element currently at
that position (if any) and any subsequent elements to the right
(increases their indices).  The new elements will appear in the Vector
in the order that they are returned by the specified Collection's
iterator.

Params:
  • index – index at which to insert the first element from the
             specified collection
  • c – elements to be inserted into this Vector
Throws:
Returns:true if this Vector changed as a result of the call
Since:1.2
/**
     * Inserts all of the elements in the specified Collection into this
     * Vector at the specified position.  Shifts the element currently at
     * that position (if any) and any subsequent elements to the right
     * (increases their indices).  The new elements will appear in the Vector
     * in the order that they are returned by the specified Collection's
     * iterator.
     *
     * @param index index at which to insert the first element from the
     *              specified collection
     * @param c elements to be inserted into this Vector
     * @return {@code true} if this Vector changed as a result of the call
     * @throws ArrayIndexOutOfBoundsException if the index is out of range
     *         ({@code index < 0 || index > size()})
     * @throws NullPointerException if the specified collection is null
     * @since 1.2
     */
    public synchronized boolean addAll(int index, Collection<? extends E> c) {
        if (index < 0 || index > elementCount)
            throw new ArrayIndexOutOfBoundsException(index);

        Object[] a = c.toArray();
        modCount++;
        int numNew = a.length;
        if (numNew == 0)
            return false;
        Object[] elementData = this.elementData;
        final int s = elementCount;
        if (numNew > elementData.length - s)
            elementData = grow(s + numNew);

        int numMoved = s - index;
        if (numMoved > 0)
            System.arraycopy(elementData, index,
                             elementData, index + numNew,
                             numMoved);
        System.arraycopy(a, 0, elementData, index, numNew);
        elementCount = s + numNew;
        return true;
    }

    
Compares the specified Object with this Vector for equality.  Returns
true if and only if the specified Object is also a List, both Lists
have the same size, and all corresponding pairs of elements in the two
Lists are equal. (Two elements e1 and e2 are equal if Objects.equals(e1, e2).) In other words, two Lists are defined to be equal if they contain the same elements in the same order. 
Params:
  • o – the Object to be compared for equality with this Vector
Returns:true if the specified Object is equal to this Vector
/**
     * Compares the specified Object with this Vector for equality.  Returns
     * true if and only if the specified Object is also a List, both Lists
     * have the same size, and all corresponding pairs of elements in the two
     * Lists are <em>equal</em>.  (Two elements {@code e1} and
     * {@code e2} are <em>equal</em> if {@code Objects.equals(e1, e2)}.)
     * In other words, two Lists are defined to be
     * equal if they contain the same elements in the same order.
     *
     * @param o the Object to be compared for equality with this Vector
     * @return true if the specified Object is equal to this Vector
     */
    public synchronized boolean equals(Object o) {
        return super.equals(o);
    }

    
Returns the hash code value for this Vector.

/**
     * Returns the hash code value for this Vector.
     */
    public synchronized int hashCode() {
        return super.hashCode();
    }

    
Returns a string representation of this Vector, containing
the String representation of each element.

/**
     * Returns a string representation of this Vector, containing
     * the String representation of each element.
     */
    public synchronized String toString() {
        return super.toString();
    }

    
Returns a view of the portion of this List between fromIndex,
inclusive, and toIndex, exclusive.  (If fromIndex and toIndex are
equal, the returned List is empty.)  The returned List is backed by this
List, so changes in the returned List are reflected in this List, and
vice-versa.  The returned List supports all of the optional List
operations supported by this List.

This method eliminates the need for explicit range operations (of
the sort that commonly exist for arrays).  Any operation that expects
a List can be used as a range operation by operating on a subList view
instead of a whole List.  For example, the following idiom
removes a range of elements from a List:

     list.subList(from, to).clear();


Similar idioms may be constructed for indexOf and lastIndexOf,
and all of the algorithms in the Collections class can be applied to
a subList.

The semantics of the List returned by this method become undefined if
the backing list (i.e., this List) is structurally modified in
any way other than via the returned List.  (Structural modifications are
those that change the size of the List, or otherwise perturb it in such
a fashion that iterations in progress may yield incorrect results.)

Params:
  • fromIndex – low endpoint (inclusive) of the subList
  • toIndex – high endpoint (exclusive) of the subList
Throws:
Returns:a view of the specified range within this List
/**
     * Returns a view of the portion of this List between fromIndex,
     * inclusive, and toIndex, exclusive.  (If fromIndex and toIndex are
     * equal, the returned List is empty.)  The returned List is backed by this
     * List, so changes in the returned List are reflected in this List, and
     * vice-versa.  The returned List supports all of the optional List
     * operations supported by this List.
     *
     * <p>This method eliminates the need for explicit range operations (of
     * the sort that commonly exist for arrays).  Any operation that expects
     * a List can be used as a range operation by operating on a subList view
     * instead of a whole List.  For example, the following idiom
     * removes a range of elements from a List:
     * <pre>
     *      list.subList(from, to).clear();
     * </pre>
     * Similar idioms may be constructed for indexOf and lastIndexOf,
     * and all of the algorithms in the Collections class can be applied to
     * a subList.
     *
     * <p>The semantics of the List returned by this method become undefined if
     * the backing list (i.e., this List) is <i>structurally modified</i> in
     * any way other than via the returned List.  (Structural modifications are
     * those that change the size of the List, or otherwise perturb it in such
     * a fashion that iterations in progress may yield incorrect results.)
     *
     * @param fromIndex low endpoint (inclusive) of the subList
     * @param toIndex high endpoint (exclusive) of the subList
     * @return a view of the specified range within this List
     * @throws IndexOutOfBoundsException if an endpoint index value is out of range
     *         {@code (fromIndex < 0 || toIndex > size)}
     * @throws IllegalArgumentException if the endpoint indices are out of order
     *         {@code (fromIndex > toIndex)}
     */
    public synchronized List<E> subList(int fromIndex, int toIndex) {
        return Collections.synchronizedList(super.subList(fromIndex, toIndex),
                                            this);
    }

    
Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive. Shifts any succeeding elements to the left (reduces their index). This call shortens the list by (toIndex - fromIndex) elements. (If toIndex==fromIndex, this operation has no effect.) 
/**
     * Removes from this list all of the elements whose index is between
     * {@code fromIndex}, inclusive, and {@code toIndex}, exclusive.
     * Shifts any succeeding elements to the left (reduces their index).
     * This call shortens the list by {@code (toIndex - fromIndex)} elements.
     * (If {@code toIndex==fromIndex}, this operation has no effect.)
     */
    protected synchronized void removeRange(int fromIndex, int toIndex) {
        modCount++;
        shiftTailOverGap(elementData, fromIndex, toIndex);
    }

    
Erases the gap from lo to hi, by sliding down following elements. 
/** Erases the gap from lo to hi, by sliding down following elements. */
    private void shiftTailOverGap(Object[] es, int lo, int hi) {
        System.arraycopy(es, hi, es, lo, elementCount - hi);
        for (int to = elementCount, i = (elementCount -= hi - lo); i < to; i++)
            es[i] = null;
    }

    
Loads a Vector instance from a stream (that is, deserializes it). This method performs checks to ensure the consistency of the fields. 
Params:
  • in – the stream
Throws:
/**
     * Loads a {@code Vector} instance from a stream
     * (that is, deserializes it).
     * This method performs checks to ensure the consistency
     * of the fields.
     *
     * @param in the stream
     * @throws java.io.IOException if an I/O error occurs
     * @throws ClassNotFoundException if the stream contains data
     *         of a non-existing class
     */
    private void readObject(ObjectInputStream in)
            throws IOException, ClassNotFoundException {
        ObjectInputStream.GetField gfields = in.readFields();
        int count = gfields.get("elementCount", 0);
        Object[] data = (Object[])gfields.get("elementData", null);
        if (count < 0 || data == null || count > data.length) {
            throw new StreamCorruptedException("Inconsistent vector internals");
        }
        elementCount = count;
        elementData = data.clone();
    }

    
Saves the state of the Vector instance to a stream (that is, serializes it). This method performs synchronization to ensure the consistency of the serialized data. 
Params:
  • s – the stream
Throws:
/**
     * Saves the state of the {@code Vector} instance to a stream
     * (that is, serializes it).
     * This method performs synchronization to ensure the consistency
     * of the serialized data.
     *
     * @param s the stream
     * @throws java.io.IOException if an I/O error occurs
     */
    private void writeObject(java.io.ObjectOutputStream s)
            throws java.io.IOException {
        final java.io.ObjectOutputStream.PutField fields = s.putFields();
        final Object[] data;
        synchronized (this) {
            fields.put("capacityIncrement", capacityIncrement);
            fields.put("elementCount", elementCount);
            data = elementData.clone();
        }
        fields.put("elementData", data);
        s.writeFields();
    }

    
Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list. The specified index indicates the first element that would be returned by an initial call to next. An initial call to previous would return the element with the specified index minus one. 
The returned list iterator is fail-fast.

Throws:
/**
     * Returns a list iterator over the elements in this list (in proper
     * sequence), starting at the specified position in the list.
     * The specified index indicates the first element that would be
     * returned by an initial call to {@link ListIterator#next next}.
     * An initial call to {@link ListIterator#previous previous} would
     * return the element with the specified index minus one.
     *
     * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public synchronized ListIterator<E> listIterator(int index) {
        if (index < 0 || index > elementCount)
            throw new IndexOutOfBoundsException("Index: "+index);
        return new ListItr(index);
    }

    
Returns a list iterator over the elements in this list (in proper
sequence).

The returned list iterator is fail-fast.

See Also:
  • listIterator(int)
/**
     * Returns a list iterator over the elements in this list (in proper
     * sequence).
     *
     * <p>The returned list iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
     *
     * @see #listIterator(int)
     */
    public synchronized ListIterator<E> listIterator() {
        return new ListItr(0);
    }

    
Returns an iterator over the elements in this list in proper sequence.

The returned iterator is fail-fast.

Returns:an iterator over the elements in this list in proper sequence
/**
     * Returns an iterator over the elements in this list in proper sequence.
     *
     * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>.
     *
     * @return an iterator over the elements in this list in proper sequence
     */
    public synchronized Iterator<E> iterator() {
        return new Itr();
    }

    
An optimized version of AbstractList.Itr

/**
     * An optimized version of AbstractList.Itr
     */
    private class Itr implements Iterator<E> {
        int cursor;       // index of next element to return
        int lastRet = -1; // index of last element returned; -1 if no such
        int expectedModCount = modCount;

        public boolean hasNext() {
            // Racy but within spec, since modifications are checked
            // within or after synchronization in next/previous
            return cursor != elementCount;
        }

        public E next() {
            synchronized (Vector.this) {
                checkForComodification();
                int i = cursor;
                if (i >= elementCount)
                    throw new NoSuchElementException();
                cursor = i + 1;
                return elementData(lastRet = i);
            }
        }

        public void remove() {
            if (lastRet == -1)
                throw new IllegalStateException();
            synchronized (Vector.this) {
                checkForComodification();
                Vector.this.remove(lastRet);
                expectedModCount = modCount;
            }
            cursor = lastRet;
            lastRet = -1;
        }

        @Override
        public void forEachRemaining(Consumer<? super E> action) {
            Objects.requireNonNull(action);
            synchronized (Vector.this) {
                final int size = elementCount;
                int i = cursor;
                if (i >= size) {
                    return;
                }
                final Object[] es = elementData;
                if (i >= es.length)
                    throw new ConcurrentModificationException();
                while (i < size && modCount == expectedModCount)
                    action.accept(elementAt(es, i++));
                // update once at end of iteration to reduce heap write traffic
                cursor = i;
                lastRet = i - 1;
                checkForComodification();
            }
        }

        final void checkForComodification() {
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
        }
    }

    
An optimized version of AbstractList.ListItr

/**
     * An optimized version of AbstractList.ListItr
     */
    final class ListItr extends Itr implements ListIterator<E> {
        ListItr(int index) {
            super();
            cursor = index;
        }

        public boolean hasPrevious() {
            return cursor != 0;
        }

        public int nextIndex() {
            return cursor;
        }

        public int previousIndex() {
            return cursor - 1;
        }

        public E previous() {
            synchronized (Vector.this) {
                checkForComodification();
                int i = cursor - 1;
                if (i < 0)
                    throw new NoSuchElementException();
                cursor = i;
                return elementData(lastRet = i);
            }
        }

        public void set(E e) {
            if (lastRet == -1)
                throw new IllegalStateException();
            synchronized (Vector.this) {
                checkForComodification();
                Vector.this.set(lastRet, e);
            }
        }

        public void add(E e) {
            int i = cursor;
            synchronized (Vector.this) {
                checkForComodification();
                Vector.this.add(i, e);
                expectedModCount = modCount;
            }
            cursor = i + 1;
            lastRet = -1;
        }
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
/**
     * @throws NullPointerException {@inheritDoc}
     */
    @Override
    public synchronized void forEach(Consumer<? super E> action) {
        Objects.requireNonNull(action);
        final int expectedModCount = modCount;
        final Object[] es = elementData;
        final int size = elementCount;
        for (int i = 0; modCount == expectedModCount && i < size; i++)
            action.accept(elementAt(es, i));
        if (modCount != expectedModCount)
            throw new ConcurrentModificationException();
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
/**
     * @throws NullPointerException {@inheritDoc}
     */
    @Override
    public synchronized void replaceAll(UnaryOperator<E> operator) {
        Objects.requireNonNull(operator);
        final int expectedModCount = modCount;
        final Object[] es = elementData;
        final int size = elementCount;
        for (int i = 0; modCount == expectedModCount && i < size; i++)
            es[i] = operator.apply(elementAt(es, i));
        if (modCount != expectedModCount)
            throw new ConcurrentModificationException();
        modCount++;
    }

    @SuppressWarnings("unchecked")
    @Override
    public synchronized void sort(Comparator<? super E> c) {
        final int expectedModCount = modCount;
        Arrays.sort((E[]) elementData, 0, elementCount, c);
        if (modCount != expectedModCount)
            throw new ConcurrentModificationException();
        modCount++;
    }

    
Creates a late-binding
and fail-fast Spliterator over the elements in this list. 
The Spliterator reports Spliterator.SIZED, Spliterator.SUBSIZED, and Spliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values. 
Returns:a Spliterator over the elements in this list
Since:1.8
/**
     * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
     * and <em>fail-fast</em> {@link Spliterator} over the elements in this
     * list.
     *
     * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
     * {@link Spliterator#SUBSIZED}, and {@link Spliterator#ORDERED}.
     * Overriding implementations should document the reporting of additional
     * characteristic values.
     *
     * @return a {@code Spliterator} over the elements in this list
     * @since 1.8
     */
    @Override
    public Spliterator<E> spliterator() {
        return new VectorSpliterator(null, 0, -1, 0);
    }

    
Similar to ArrayList Spliterator 
/** Similar to ArrayList Spliterator */
    final class VectorSpliterator implements Spliterator<E> {
        private Object[] array;
        private int index; // current index, modified on advance/split
        private int fence; // -1 until used; then one past last index
        private int expectedModCount; // initialized when fence set

        
Creates new spliterator covering the given range. 
/** Creates new spliterator covering the given range. */
        VectorSpliterator(Object[] array, int origin, int fence,
                          int expectedModCount) {
            this.array = array;
            this.index = origin;
            this.fence = fence;
            this.expectedModCount = expectedModCount;
        }

        private int getFence() { // initialize on first use
            int hi;
            if ((hi = fence) < 0) {
                synchronized (Vector.this) {
                    array = elementData;
                    expectedModCount = modCount;
                    hi = fence = elementCount;
                }
            }
            return hi;
        }

        public Spliterator<E> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid) ? null :
                new VectorSpliterator(array, lo, index = mid, expectedModCount);
        }

        @SuppressWarnings("unchecked")
        public boolean tryAdvance(Consumer<? super E> action) {
            Objects.requireNonNull(action);
            int i;
            if (getFence() > (i = index)) {
                index = i + 1;
                action.accept((E)array[i]);
                if (modCount != expectedModCount)
                    throw new ConcurrentModificationException();
                return true;
            }
            return false;
        }

        @SuppressWarnings("unchecked")
        public void forEachRemaining(Consumer<? super E> action) {
            Objects.requireNonNull(action);
            final int hi = getFence();
            final Object[] a = array;
            int i;
            for (i = index, index = hi; i < hi; i++)
                action.accept((E) a[i]);
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
        }

        public long estimateSize() {
            return getFence() - index;
        }

        public int characteristics() {
            return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
        }
    }

    void checkInvariants() {
        // assert elementCount >= 0;
        // assert elementCount == elementData.length || elementData[elementCount] == null;
    }
}