de.schlichtherle.truezip.util.JointIterator Maven / Gradle / Ivy

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/*
 * Copyright (C) 2005-2015 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package de.schlichtherle.truezip.util;

import java.util.Iterator;
import java.util.NoSuchElementException;
import javax.annotation.concurrent.NotThreadSafe;

/**
 * An iterator which concatenates the elements of two other iterators.
 *
 * @param    The type of the elements.
 * @author  Christian Schlichtherle
 */
@NotThreadSafe
public final class JointIterator implements Iterator {
    private Iterator i1, i2;

    /**
     * Constructs a new {@code JointIterator} from the given iterators.
     *
     * @param  i1 the first iterator.
     * @param  i2 the second iterator.
     * @throws NullPointerException if any parameter is {@code null}.
     */
    public JointIterator(
            final Iterator i1,
            final Iterator i2) {
        if (i1 == null || i2 == null)
            throw new NullPointerException();
        this.i1 = i1;
        this.i2 = i2;
    }

    /**
     * Constructs a new {@code JointIterator} from the given iterables.
     *
     * @param  i1 the first iterable.
     * @param  i2 the second iterable.
     * @throws NullPointerException if any parameter is {@code null}.
     */
    public JointIterator(
            final Iterable i1,
            final Iterable i2) {
        this.i1 = i1.iterator();
        this.i2 = i2.iterator();
    }

    @Override
    public boolean hasNext() {
        return i1.hasNext()
           || (i1 != i2 && (i1 = i2).hasNext());
    }

    @Override
    public E next() {
        try {
            return i1.next();
        } catch (NoSuchElementException ex) {
            if (i1 == i2)
                throw ex;
            return (i1 = i2).next();
        }
    }

    @Override
    public void remove() {
        i1.remove();
    }
}