com.google.cloud.dataflow.sdk.util.state.CombiningState Maven / Gradle / Ivy

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Google Cloud Dataflow Java SDK provides a simple, Java-based interface for processing virtually any size data using Google cloud resources. This artifact includes entire Dataflow Java SDK.

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/*
 * Copyright (C) 2015 Google Inc.
 *
 * Licensed 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 com.google.cloud.dataflow.sdk.util.state;

import com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn;

/**
 * State that combines multiple {@code InputT} values using a {@link CombineFn} to produce a single
 * {@code OutputT} value.
 *
 * @param  the type of values added to the state
 * @param  the type of value extracted from the state
 */
public interface CombiningState extends ReadableState, State {
  /**
   * Add a value to the buffer.
   */
  void add(InputT value);

  /**
   * Return true if this state is empty.
   */
  ReadableState isEmpty();

  @Override
  CombiningState readLater();
}