vector.java

已经移植好的java虚拟机

/*
 * Copyright 1995-2002 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 * Use is subject to license terms.
 */

package java.util;

/**
 * The <code>Vector</code> 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</code> can grow or shrink as needed to accommodate
 * adding and removing items after the <code>Vector</code> has been created.
 * <p>
 * Each vector tries to optimize storage management by maintaining a
 * <code>capacity</code> and a <code>capacityIncrement</code>. The
 * <code>capacity</code> 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</code>. An application can increase the
 * capacity of a vector before inserting a large number of
 * components; this reduces the amount of incremental reallocation.
 * <p>
 * Note: To conserve space, the CLDC implementation
 * is based on JDK 1.1.8, not JDK 1.3.
 *
 * @author  Lee Boynton
 * @author  Jonathan Payne
 * @version 1.39, 07/01/98 (CLDC 1.0, Spring 2000)
 * @since   JDK1.0, CLDC 1.0
 */
public
class Vector {

    /**
     * The array buffer into which the components of the vector are
     * stored. The capacity of the vector is the length of this array buffer.
     *
     * @since   JDK1.0
     */
    protected Object elementData[];

    /**
     * The number of valid components in the vector.
     *
     * @since   JDK1.0
     */
    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 <code>0</code>, the capacity of the
     * vector is doubled each time it needs to grow.
     *
     * @since   JDK1.0
     */
    protected int capacityIncrement;

    /**
     * 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.
     * @exception 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.
     *
     * @param   initialCapacity   the initial capacity of the vector.
     * @since   JDK1.0
     */
    public Vector(int initialCapacity) {
        this(initialCapacity, 0);
    }

    /**
     * Constructs an empty vector.
     *
     * @since   JDK1.0
     */
    public Vector() {
        this(10);
    }

    /**
     * Copies the components of this vector into the specified array.
     * The array must be big enough to hold all the objects in this  vector.
     *
     * @param   anArray   the array into which the components get copied.
     * @since   JDK1.0
     */
    public synchronized void copyInto(Object anArray[]) {
        int i = elementCount;
        while (i-- > 0) {
            anArray[i] = elementData[i];
        }
    }

    /**
     * Trims the capacity of this vector to be the vector's current
     * size. An application can use this operation to minimize the
     * storage of a vector.
     *
     * @since   JDK1.0
     */
    public synchronized void trimToSize() {
        int oldCapacity = elementData.length;
        if (elementCount < oldCapacity) {
            Object oldData[] = elementData;
            elementData = new Object[elementCount];
            System.arraycopy(oldData, 0, elementData, 0, 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.
     *
     * @param   minCapacity   the desired minimum capacity.
     * @since   JDK1.0
     */
    public synchronized void ensureCapacity(int minCapacity) {
        if (minCapacity > elementData.length) {
            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 java.util.Vector#ensureCapacity(int)
     */
    private void ensureCapacityHelper(int minCapacity) {
        int oldCapacity = elementData.length;
        Object oldData[] = elementData;
        int newCapacity = (capacityIncrement > 0) ?
            (oldCapacity + capacityIncrement) : (oldCapacity * 2);
        if (newCapacity < minCapacity) {
            newCapacity = minCapacity;
        }
        elementData = new Object[newCapacity];
        System.arraycopy(oldData, 0, elementData, 0, elementCount);
    }

    /**
     * Sets the size of this vector. If the new size is greater than the
     * current size, new <code>null</code> 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</code> and greater are discarded.
     *
     * @param   newSize   the new size of this vector.
     * @since   JDK1.0
     */
    public synchronized void setSize(int newSize) {
        if ((newSize > elementCount) && (newSize > elementData.length)) {
            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 of this vector.
     * @since   JDK1.0
     */
    public int capacity() {
        return elementData.length;
    }

    /**
     * Returns the number of components in this vector.
     *
     * @return  the number of components in this vector.
     * @since   JDK1.0
     */
    public int size() {
        return elementCount;
    }

    /**
     * Tests if this vector has no components.
     *
     * @return  <code>true</code> if this vector has no components;
     *          <code>false</code> otherwise.
     * @since   JDK1.0
     */
    public boolean isEmpty() {
        return elementCount == 0;
    }

    /**
     * Returns an enumeration of the components of this vector.
     *
     * @return  an enumeration of the components of this vector.
     * @see     java.util.Enumeration
     * @since   JDK1.0
     */
    public synchronized Enumeration elements() {
        return new VectorEnumerator(this);
    }

    /**
     * Tests if the specified object is a component in this vector.
     *
     * @param   elem   an object.
     * @return  <code>true</code> if the specified object is a component in
     *          this vector; <code>false</code> otherwise.
     * @since   JDK1.0
     */
    public boolean contains(Object elem) {
        return indexOf(elem, 0) >= 0;
    }

    /**
     * Searches for the first occurence of the given argument, testing
     * for equality using the <code>equals</code> method.
     *
     * @param   elem   an object.
     * @return  the index of the first occurrence of the argument in this
     *          vector; returns <code>-1</code> if the object is not found.
     * @see     java.lang.Object#equals(java.lang.Object)
     * @since   JDK1.0
     */
    public int indexOf(Object elem) {
        return indexOf(elem, 0);
    }

    /**
     * Searches for the first occurence of the given argument, beginning
     * the search at <code>index</code>, and testing for equality using
     * the <code>equals</code> method.
     *
     * @param   elem    an object.
     * @param   index   the index to start searching from.
     * @return  the index of the first occurrence of the object argument in
     *          this vector at position <code>index</code> or later in the
     *          vector; returns <code>-1</code> if the object is not found.
     * @see     java.lang.Object#equals(java.lang.Object)
     * @since   JDK1.0
     */
    public synchronized int indexOf(Object elem, int index) {
        if (elem == null) {
            for (int i = index ; i < elementCount ; i++)
                if (elementData[i]==null)
                    return i;
        } else {
            for (int i = index ; i < elementCount ; i++)
                if (elem.equals(elementData[i]))
                    return i;
        }