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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * 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 com.rapiddweller.common.iterator;

import java.util.Iterator;

/**
 * {@link Iterator} implementation which allows to preview the {@link #next()} value
 * without actually consuming it using the {@link #peek()} method.
 * Created: 25.01.2012 14:11:17
 *
 * @param  the type to iterate
 * @author Volker Bergmann
 * @since 0.5.14
 */
public class PreviewIterator extends IteratorProxy {

  private boolean hasNext;
  private E next;

  /**
   * Instantiates a new Preview iterator.
   *
   * @param source the source
   */
  public PreviewIterator(Iterator source) {
    super(source);
    fetchNext();
  }

  /**
   * Peek e.
   *
   * @return the e
   */
  public E peek() {
    return this.next;
  }

  // Iterator interface implementation -------------------------------------------------------------------------------

  @Override
  public boolean hasNext() {
    return hasNext;
  }

  @Override
  public E next() {
    E result = this.next;
    fetchNext();
    return result;
  }

  // private helpers -------------------------------------------------------------------------------------------------

  private void fetchNext() {
    this.hasNext = source.hasNext();
    this.next = (this.hasNext ? source.next() : null);
  }

}