vector.java

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/*
 * @(#)Vector.java	1.38 97/12/18
 * 
 * Copyright (c) 1995, 1996 Sun Microsystems, Inc. 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.
 * 
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * 
 * CopyrightVersion 1.1_beta
 * 
 */

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. 
 *
 * @author  Lee Boynton
 * @author  Jonathan Payne
 * @version 1.38, 12/18/97
 * @since   JDK1.0
 */
public
class Vector implements 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.
     *
     * @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;

    /** 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.
     * @since   JDK1.0
     */
    public Vector(int initialCapacity, int capacityIncrement) {
	super();
	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 final 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 final 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 final 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 final 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 final 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 final 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 final 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 final 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 final 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 final 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 final synchronized int indexOf(Object elem, int index) {
	for (int i = index ; i < elementCount ; i++) {
	    if (elem.equals(elementData[i])) {
		return i;
	    }
	}
	return -1;
    }