/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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package com.sun.xml.internal.bind.v2.util;

import java.util.Iterator;

import java.util.Map;

import java.util.NoSuchElementException;

/**

 * {@link Iterator} that walks over a map of maps.

 *

 * @author Kohsuke Kawaguchi

 * @since 2.0

 */

public final class FlattenIterator<T> implements Iterator<T> {

    private final Iterator<? extends Map<?,? extends T>> parent;

    private Iterator<? extends T> child = null;

    private T next;

    public FlattenIterator( Iterable<? extends Map<?,? extends T>> core ) {

        this.parent = core.iterator();

    }

    public void remove() {

        throw new UnsupportedOperationException();

    }

    public boolean hasNext() {

        getNext();

        return next!=null;

    }

    public T next() {

        T r = next;

        next = null;

        if(r==null)

            throw new NoSuchElementException();

        return r;

    }

    private void getNext() {

        if(next!=null)  return;

        if(child!=null && child.hasNext()) {

            next = child.next();

            return;

        }

        // child is empty

        if(parent.hasNext()) {

            child = parent.next().values().iterator();

            getNext();

        }

        // else

        //      no more object

    }

}