heron/api/src/java/org/apache/heron/api/Pair.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.heron.api;

import java.io.Serializable;

/**
 * A pair of values.
 *
 * @param <T1> the type of the first value
 * @param <T2> the type of the second value
 */
public final class Pair<T1, T2> implements Serializable {

  private static final long serialVersionUID = 3926373357946515821L;
  /**
   * The first value
   */
  private final T1 first;
  /**
   * The second value
   */
  private final T2 second;

  /**
   * Constructs a new pair of values
   *
   * @param first the first value
   * @param second the second value
   */
  private Pair(T1 first, T2 second) {
    this.first = first;
    this.second = second;
  }

  /**
   * Returns the first value in a pair.
   *
   * @return the first value
   */
  public T1 getFirst() {
    return first;
  }

  /**
   * Returns the second value in a pair.
   *
   * @return the second value
   */
  public T2 getSecond() {
    return second;
  }

  /**
   * Constructs a new pair of values.
   *
   * @param first the first value
   * @param second the second value
   * @param <T1> the type of the first value
   * @param <T2> the type of the second value
   * @return a new pair of values
   */
  public static <T1, T2> Pair<T1, T2> of(T1 first, T2 second) {
    return new Pair<>(first, second);
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    Pair<?, ?> pair = (Pair<?, ?>) o;

    if (first != null ? !first.equals(pair.first) : pair.first != null) {
      return false;
    }
    return second != null ? second.equals(pair.second) : pair.second == null;

  }

  @Override
  public int hashCode() {
    int result = first != null ? first.hashCode() : 0;
    result = 31 * result + (second != null ? second.hashCode() : 0);
    return result;
  }

  @Override
  public String toString() {
    return "(" + first + ", " + second + ')';
  }
}