CompoundEnumeration.java

/*
 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Contributors:
 *     bstefanescu
 */
package org.nuxeo.osgi.util;

import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
 */
public class CompoundEnumeration<E> implements Enumeration<E> {

    private final Enumeration<E>[] enums;

    private int index = 0;

    @SuppressWarnings("unchecked")
    public CompoundEnumeration(Enumeration<?>[] enums) {
        this.enums = (Enumeration<E>[]) enums;
    }

    private boolean next() {
        while (index < enums.length) {
            if (enums[index] != null && enums[index].hasMoreElements()) {
                return true;
            }
            index++;
        }
        return false;
    }

    @Override
    public boolean hasMoreElements() {
        return next();
    }

    @Override
    public E nextElement() {
        if (!next()) {
            throw new NoSuchElementException();
        }
        return enums[index].nextElement();
    }

}