arrayiterator.java

jsr170接口的java实现。是个apache的开源项目。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.jackrabbit.rmi.remote;

import java.io.Serializable;
import java.util.NoSuchElementException;

/**
 * A simple array-based remote iterator. Used when the iteration is
 * short enough for all the elements to be sent over the network in
 * one go.
 */
public class ArrayIterator implements RemoteIterator, Serializable {

    /**
     * The elements in this iterator. Set to <code>null</code> when
     * all elements have been iterated.
     */
    private Object[] elements;

    /**
     * The position of this iterator. Set to the size of the iterator
     * when all elements have been iterated.
     */
    private int position;

    /**
     * Creates an array-based remote iterator from the given array
     * of remote references or serializable objects.
     *
     * @param elements elements of the iteration
     */
    public ArrayIterator(Object[] elements) {
        this.elements = elements;
        this.position = 0;
    }

    /**
     * Returns the size of the iterator.
     *
     * @return length of the iterator
     * @see RemoteIterator#getSize()
     */
    public long getSize() {
        if (elements == null) {
            return position;
        } else {
            return elements.length;
        }
    }

    /**
     * Skips the first <code>items</code> elements in the array.
     * {@inheritDoc}
     */
    public void skip(long items)
            throws IllegalArgumentException, NoSuchElementException {
        if (items < 0) {
            throw new IllegalArgumentException("Negative skip is not allowed");
        } else if (elements == null || items > elements.length) {
            throw new NoSuchElementException("Skipped past the last element");
        } else {
            Object[] tmp = new Object[elements.length - (int) items];
            System.arraycopy(elements, (int) items, tmp, 0, tmp.length);
            elements = tmp;
            position += items;
        }
    }

    /**
     * Returns the underlying array.
     * {@inheritDoc}
     */
    public Object[] nextObjects() throws IllegalArgumentException {
        if (elements == null) {
            return null;
        } else {
            Object[] tmp = elements;
            position += elements.length;
            elements = null;
            return tmp;
        }
    }

}