content: /*
   * 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.beam.sdk.fn.stream;
  
  import java.util.Iterator;
  
  /** {@link Iterator} that supports prefetching the next set of records. */
  public interface PrefetchableIterator<T> extends Iterator<T> {
  
    /**
     * Returns {@code true} if and only if {@link #hasNext} and {@link #next} will not require an
     * expensive operation.
     */
    boolean isReady();
  
    /**
     * If not {@link #isReady}, schedules the next expensive operation such that at some point in time
     * in the future {@link #isReady} will return true.
     */
    void prefetch();
  }
  