arrayenumerator.java

java高级使用教程 全书一共分六章

// ArrayEnumerator - Enumeration for an array of objects
//
// Copyright (C) 1996 by Jef Poskanzer <[e-mail]>.  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme;

import java.util.*;

/// Enumeration for an array of objects
// <P>
// Vectors come with a method to make an Enumeration, but if you're
// using arrays instead of Vectors you don't get that.
// Instead you can use this class to make an Enumeration for any array
// of Objects.
// It returns the contents of the array in order,
// optionally skipping any null elements.
// <P>
// <A HREF="/resources/classes/Acme/ArrayEnumerator.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class ArrayEnumerator implements Enumeration
    {

    private Object[] objects;

    private boolean skipNulls;
    private int i;
    private int next;
    private boolean foundNext;

    public ArrayEnumerator( Object[] objects )
	{
	this( objects, false );
	}

    public ArrayEnumerator( Object[] objects, boolean skipNulls )
	{
	this.skipNulls = skipNulls;
	this.objects = objects;
	i = -1;
	foundNext = false;
	}

    public boolean hasMoreElements()
	{
	findNextElement();
	return next != -1;
	}
    
    public Object nextElement()
	{
	findNextElement();
	if ( next == -1 )
	    throw new NoSuchElementException( "ArrayEnumerator" );
	i = next;
	foundNext = false;
	return objects[i];
	}

    private void findNextElement()
	{
	if ( foundNext )
	    return;
	foundNext = true;
	for ( next = i + 1; next < objects.length; ++next )
	    if ( objects[next] != null || ! skipNulls )
		return;
	next = -1;
	}

    }