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

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

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 *

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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;

import jdk.internal.util.ArraysSupport;

/**

 * 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.

     *

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

     *

     * @serial

     */

    @SuppressWarnings("serial") // Conditionally serializable

    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 */

    @java.io.Serial

    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) {

        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 {@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++;

            if (minCapacity > elementData.length)

                grow(minCapacity);

        }

    }

    /**

     * 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) {

        int oldCapacity = elementData.length;

        int newCapacity = ArraysSupport.newLength(oldCapacity,

                minCapacity - oldCapacity, /* minimum growth */

                capacityIncrement > 0 ? capacityIncrement : oldCapacity

                                           /* preferred growth */);

        return elementData = Arrays.copyOf(elementData, newCapacity);

    }

    private Object[] grow() {

        return grow(elementCount + 1);

    }

    /**

     * 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.

     *

     * @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. 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 {@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 {@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 {@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 {@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 {@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.

     *

     * <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() - 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 {@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) {

        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 {@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.

     *

     * <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.

     *

     * <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() {

        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 {@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

     */

    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 <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.

     *

     * @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;

    }

    /**

     * 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.

     *

     * @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

     * {@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).

     *

     * @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.

     *

     * @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

     */

    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 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.

     *

     * @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.

     *

     * @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}

     */

    @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.

     *

     * @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 <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.

     */

    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++;

        shiftTailOverGap(elementData, fromIndex, toIndex);

    }

    /** 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 {@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

     */

    @java.io.Serial

    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 {@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

     */

    @java.io.Serial

    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 {@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;