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TrueZIP is a Java based Virtual File System (VFS) to enable transparent, multi-threaded read/write access to archive files (ZIP, TAR etc.) as if they were directories. Archive files may be arbitrarily nested and the nesting level is only limited by heap and file system size.

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/*
 * Copyright (C) 2007-2010 Schlichtherle IT Services
 *
 * 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.
 */

package de.schlichtherle.util;

import java.util.*;

/**
 * Concatenates two enumerations.
 *
 * @author Christian Schlichtherle
 * @version $Id$
 * @since TrueZIP 6.5
 */
public final class JointEnumeration implements Enumeration {
    private Enumeration e1;
    private final Enumeration e2;

    public JointEnumeration(final Enumeration e1, final Enumeration e2) {
        this.e1 = e1;
        this.e2 = e2;
    }

    public boolean hasMoreElements() {
        return e1.hasMoreElements()
           || (e1 != e2 && (e1 = e2).hasMoreElements());
    }

    public Object nextElement() {
        try {
            return e1.nextElement();
        } catch (NoSuchElementException ex) {
            if (e1 == e2)
                throw ex;
            return (e1 = e2).nextElement();
        }
    }
}




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