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.runners.spark.io;
  
  import java.io.IOException;
  import java.io.Serializable;
  import org.apache.beam.sdk.io.UnboundedSource;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Passing null values to Spark's Java API may cause problems because of Guava preconditions. See:
   * {@link org.apache.spark.api.java.JavaUtils#optionToOptional}
   */
  public class EmptyCheckpointMark implements UnboundedSource.CheckpointMark, Serializable {
    private static final EmptyCheckpointMark INSTANCE = new EmptyCheckpointMark();
    private static final int ID = 2654265; // some constant to serve as identifier.
  
    private EmptyCheckpointMark() {}
  
    public static EmptyCheckpointMark get() {
      return INSTANCE;
    }
  
    @Override
    public void finalizeCheckpoint() throws IOException {}
  
    @Override
    public boolean equals(@Nullable Object obj) {
      return obj instanceof EmptyCheckpointMark;
    }
  
    @Override
    public int hashCode() {
      return ID;
    }
  }
  