api/src/main/java/org/apache/iceberg/io/ClosingIterator.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.iceberg.io;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Iterator;

/**
 * A convenience wrapper around {@link CloseableIterator}, providing auto-close
 * functionality when all of the elements in the iterator are consumed.
 */
public class ClosingIterator<T> implements Iterator<T> {
  private final CloseableIterator<T> iterator;
  private boolean isClosed;

  public ClosingIterator(CloseableIterator<T> iterator) {
    this.iterator = iterator;
  }

  @Override
  public boolean hasNext() {
    boolean hasNext = iterator.hasNext();
    if (!hasNext && !isClosed) {
      close();
    }
    return hasNext;
  }

  @Override
  public T next() {
    return iterator.next();
  }

  private void close() {
    try {
      iterator.close();
      isClosed = true;
    } catch (IOException e) {
      throw new UncheckedIOException(e);
    }
  }
}