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/*
 * 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 com.feilong.lib.collection4.iterators;

import java.util.NoSuchElementException;

import org.apache.commons.collections4.ResettableIterator;

/**
 * SingletonIterator is an {@link java.util.Iterator} over a single
 * object instance.
 * 
 * @param 
 *
 * @since 2.0
 */
public class SingletonIterator implements ResettableIterator{

    /** Whether remove is allowed */
    private final boolean removeAllowed;

    /** Is the cursor before the first element */
    private boolean       beforeFirst = true;

    /** Has the element been removed */
    private boolean       removed     = false;

    /** The object */
    private E             object;

    /**
     * Constructs a new SingletonIterator where remove
     * is a permitted operation.
     *
     * @param object
     *            the single object to return from the iterator
     */
    public SingletonIterator(final E object){
        this(object, true);
    }

    /**
     * Constructs a new SingletonIterator optionally choosing if
     * remove is a permitted operation.
     *
     * @param object
     *            the single object to return from the iterator
     * @param removeAllowed
     *            true if remove is allowed
     * @since 3.1
     */
    public SingletonIterator(final E object, final boolean removeAllowed){
        super();
        this.object = object;
        this.removeAllowed = removeAllowed;
    }

    //-----------------------------------------------------------------------
    /**
     * Is another object available from the iterator?
     * 

* This returns true if the single object hasn't been returned yet. * * @return true if the single object hasn't been returned yet */ @Override public boolean hasNext(){ return beforeFirst && !removed; } /** * Get the next object from the iterator. *

* This returns the single object if it hasn't been returned yet. * * @return the single object * @throws NoSuchElementException * if the single object has already * been returned */ @Override public E next(){ if (!beforeFirst || removed){ throw new NoSuchElementException(); } beforeFirst = false; return object; } /** * Remove the object from this iterator. * * @throws IllegalStateException * if the {@code next} method has not * yet been called, or the {@code remove} method has already * been called after the last call to the {@code next} * method. * @throws UnsupportedOperationException * if remove is not supported */ @Override public void remove(){ if (removeAllowed){ if (removed || beforeFirst){ throw new IllegalStateException(); } object = null; removed = true; }else{ throw new UnsupportedOperationException(); } } /** * Reset the iterator to the start. */ @Override public void reset(){ beforeFirst = true; } }





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