qdg.bits.ConcatIterator.java Source code

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Here is the source code for qdg.bits.ConcatIterator.java

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/*
 * Copyright (C) 2013 Marton Makai
 *
 * 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 qdg.bits;

import java.util.Iterator;
import java.util.NoSuchElementException;

import com.google.common.collect.UnmodifiableIterator;

/**
 * Combines multiple iterators into an single unmodifiable iterator.
 * 
 * Though com.google.common.collect.Iterators provides a general way to
 * combine iterators, its special case for combining 2, 3 or 4
 * iterators just calls the general implementation. A specialization
 * for 2 iterators can be slightly faster for several applications.
 *
 * @param <T>
 */
public class ConcatIterator<T> extends UnmodifiableIterator<T> {

    private Iterator<T> i0, i1;

    public ConcatIterator(Iterator<T> i0, Iterator<T> i1) {
        this.i0 = i0;
        this.i1 = i1;
    }

    @Override
    public boolean hasNext() {
        return i0.hasNext() || i1 != null && i1.hasNext();
    }

    @Override
    public T next() {
        if (i0.hasNext()) {
            return i0.next();
        } else if (i1 != null) {
            i0 = i1;
            i1 = null;
            if (i0.hasNext()) {
                return i0.next();
            } else {
                throw new NoSuchElementException();
            }
        } else {
            throw new NoSuchElementException();
        }
    }
}