common/src/main/java/org/apache/nemo/common/ir/BoundedIteratorReadable.java

/*
 * 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.nemo.common.ir;

import java.util.Iterator;

/**
 * An abstract readable class that retrieves data from iterator.
 *
 * @param <O> output type.
 */
public abstract class BoundedIteratorReadable<O> implements Readable<O> {

  private Iterator<O> iterator;

  /**
   * Initialize iterator.
   *
   * @return iterator
   */
  protected abstract Iterator<O> initializeIterator();

  /**
   * Prepare reading data.
   */
  @Override
  public final void prepare() {
    iterator = initializeIterator();
  }

  @Override
  public final O readCurrent() {
    return iterator.next();
  }

  @Override
  public final boolean isFinished() {
    return !iterator.hasNext();
  }
}