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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  *

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 package java.util;

 /**

  * 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><a name="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.

  *

  * <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}/../technotes/guides/collections/index.html">

  * 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}.

  *

  * @author  Lee Boynton

  * @author  Jonathan Payne

  * @see Collection

  * @see LinkedList

  * @since   JDK1.0

  */

 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.

      *

      * <p>Any array elements following the last element in the Vector are null.

      *

      * @serial

      */

     protected Object[] elementData;

     /**

      * 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

      */

     protected int capacityIncrement;

     /** 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.

      *

      * @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.

      *

      * @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 {@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.

      *

      * @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) {

         elementData = c.toArray();

         elementCount = elementData.length;

         // c.toArray might (incorrectly) not return Object[] (see 6260652)

         if (elementData.getClass() != Object[].class)

             elementData = Arrays.copyOf(elementData, elementCount, Object[].class);

     }

     /**

      * 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 {@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.

      *

      * <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++;

             ensureCapacityHelper(minCapacity);

         }

     }

     /**

      * This implements the unsynchronized semantics of ensureCapacity.

      * Synchronized methods in this class can internally call this

      * method for ensuring capacity without incurring the cost of an

      * extra synchronization.

      *

      * @see #ensureCapacity(int)

      */

     private void ensureCapacityHelper(int minCapacity) {

         // overflow-conscious code

         if (minCapacity - elementData.length > 0)

             grow(minCapacity);

     }

     /**

      * The maximum size of array to allocate.

      * 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;

     private void grow(int minCapacity) {

         // overflow-conscious code

         int oldCapacity = elementData.length;

         int newCapacity = oldCapacity + ((capacityIncrement > 0) ?

                                          capacityIncrement : oldCapacity);

         if (newCapacity - minCapacity < 0)

             newCapacity = minCapacity;

         if (newCapacity - MAX_ARRAY_SIZE > 0)

             newCapacity = hugeCapacity(minCapacity);

         elementData = Arrays.copyOf(elementData, newCapacity);

     }

     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 {@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 > elementCount) {

             ensureCapacityHelper(newSize);

         } else {

             for (int i = newSize ; i < elementCount ; i++) {

                 elementData[i] = null;

             }

         }

         elementCount = newSize;

     }

     /**

      * 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.

      *

      * @return  the number of components in this vector

      */

     public synchronized int size() {

         return elementCount;

     }

     /**

      * 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 {@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.

      *

      * @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 {@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

      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.

      *

      * @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 {@code i} such that

      * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,

      * 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 {@code index}, or returns -1 if

      * the element is not found.

      * More formally, returns the lowest index {@code i} such that

      * <tt>(i&nbsp;&gt;=&nbsp;index&nbsp;&amp;&amp;&nbsp;(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i))))</tt>,

      * 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 {@code i} such that

      * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,

      * 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 {@code index}, or returns -1 if

      * the element is not found.

      * More formally, returns the highest index {@code i} such that

      * <tt>(i&nbsp;&lt;=&nbsp;index&nbsp;&amp;&amp;&nbsp;(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i))))</tt>,

      * 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.

      *

      * <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 {@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.

      *

      * @return  the last component of the vector, i.e., the component at index

      *          <code>size()&nbsp;-&nbsp;1</code>.

      * @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 {@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

      * {@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) {

         modCount++;

         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);

         }

         elementCount--;

         elementData[elementCount] = null; /* to let gc do its work */

     }

     /**

      * 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) {

         modCount++;

         if (index > elementCount) {

             throw new ArrayIndexOutOfBoundsException(index

                                                      + " > " + elementCount);

         }

         ensureCapacityHelper(elementCount + 1);

         System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);

         elementData[index] = obj;

         elementCount++;

     }

     /**

      * 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++;

         ensureCapacityHelper(elementCount + 1);

         elementData[elementCount++] = obj;

     }

     /**

      * 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.

      *

      * <p>This method is identical in functionality to the {@link #clear}

      * method (which is part of the {@link List} interface).

      */

     public synchronized void removeAllElements() {

         modCount++;

         // Let gc do its work

         for (int i = 0; i < elementCount; i++)

             elementData[i] = null;

         elementCount = 0;

     }

     /**

      * 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();

         }

     }

     /**

      * 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.

      *

      * <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 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 is not a supertype

      * of the runtime type 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];

     }

     /**

      * 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.

      *

      * @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;

     }

     /**

      * 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++;

         ensureCapacityHelper(elementCount + 1);

         elementData[elementCount++] = e;

         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

      * {@code (o==null ? get(i)==null : o.equals(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).

      *

      * @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.

      *

      * @throws ArrayIndexOutOfBoundsException if the index is out of range

      *         ({@code index < 0 || index >= size()})

      * @param index the index of the element to be removed

      * @return element that was removed

      * @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

      */

     public void clear() {

         removeAllElements();

     }

     // Bulk Operations

     /**

      * 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.)

      *

      * @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 synchronized boolean addAll(Collection<? extends E> c) {

         modCount++;

         Object[] a = c.toArray();

         int numNew = a.length;

         ensureCapacityHelper(elementCount + numNew);

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

         elementCount += numNew;

         return numNew != 0;

     }

     /**

      * 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 synchronized boolean removeAll(Collection<?> c) {

         return super.removeAll(c);

     }

     /**

      * 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 synchronized boolean retainAll(Collection<?> c) {

         return super.retainAll(c);

     }

     /**

      * 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) {

         modCount++;

         if (index < 0 || index > elementCount)

             throw new ArrayIndexOutOfBoundsException(index);

         Object[] a = c.toArray();

         int numNew = a.length;

         ensureCapacityHelper(elementCount + numNew);

         int numMoved = elementCount - index;

         if (numMoved > 0)

             System.arraycopy(elementData, index, elementData, index + numNew,

                              numMoved);

         System.arraycopy(a, 0, elementData, index, numNew);

         elementCount += numNew;

         return numNew != 0;

     }

     /**

      * 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 (e1==null ? e2==null :

      * e1.equals(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.

      */

     public synchronized int hashCode() {

         return super.hashCode();

     }

     /**

      * 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.

      *

      * <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

      * {@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++;

         int numMoved = elementCount - toIndex;

         System.arraycopy(elementData, toIndex, elementData, fromIndex,

                          numMoved);

         // Let gc do its work

         int newElementCount = elementCount - (toIndex-fromIndex);

         while (elementCount != newElementCount)

             elementData[--elementCount] = null;

     }

     /**

      * 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).

      *

      * <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.

      *

      * <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

      */

     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;

         }

         final void checkForComodification() {

             if (modCount != expectedModCount)

                 throw new ConcurrentModificationException();

         }

     }

     /**

      * 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;

         }

     }

 }