/*
 * @(#)ResourceBundleEnumeration.java	1.5 04/05/05
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util;

/**
 * Implements an Enumeration that combines elements from a Set and
 * an Enumeration. Used by ListResourceBundle and PropertyResourceBundle.
 */
class ResourceBundleEnumeration implements Enumeration<String> {

    Set<String> set;
    Iterator<String> iterator;
    Enumeration<String> enumeration; // may remain null

    /**
     * Constructs a resource bundle enumeration.
     * @param set an set providing some elements of the enumeration
     * @param enumeration an enumeration providing more elements of the enumeration.
     *        enumeration may be null.
     */
    ResourceBundleEnumeration(Set<String> set, Enumeration<String> enumeration) {
        this.set = set;
        this.iterator = set.iterator();
        this.enumeration = enumeration;
    }

    String next = null;
            
    public boolean hasMoreElements() {
        if (next == null) {
            if (iterator.hasNext()) {
                next = iterator.next();
            } else if (enumeration != null) {
                while (next == null && enumeration.hasMoreElements()) {
                    next = enumeration.nextElement();
                    if (set.contains(next)) {
                        next = null;
                    }
                }
            }
        }
        return next != null;
    }

    public String nextElement() {
        if (hasMoreElements()) {
            String result = next;
            next = null;
            return result;
        } else {
            throw new NoSuchElementException();
        }
    }
}