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.values;
  
  import java.util.Collections;
  import java.util.Map;
  import org.apache.beam.sdk.Pipeline;
  import org.apache.beam.sdk.io.WriteFiles;
  import org.apache.beam.sdk.transforms.PTransform;
  
  /**
   * {@link PDone} is the output of a {@link PTransform} that has a trivial result, such as a {@link
   * WriteFiles}.
   */
  public class PDone implements POutput {
  
    private final Pipeline pipeline;
  
    private PDone(Pipeline pipeline) {
      this.pipeline = pipeline;
    }
  
    /** Creates a {@link PDone} in the given {@link Pipeline}. */
    public static PDone in(Pipeline pipeline) {
      return new PDone(pipeline);
    }
  
    @Override
    public Pipeline getPipeline() {
      return pipeline;
    }
  
    /** A {@link PDone} contains no {@link PValue PValues}. */
    @Override
    public Map<TupleTag<?>, PValue> expand() {
      return Collections.emptyMap();
    }
  
    /** Does nothing; there is nothing to finish specifying. */
    @Override
    public void finishSpecifyingOutput(
        String transformName, PInput input, PTransform<?, ?> transform) {}
  }
  