001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.util;
019
020import java.io.Serializable;
021import org.apache.yetus.audience.InterfaceAudience;
022
023/**
024 * A generic class for pairs.
025 * @param <T1>
026 * @param <T2>
027 */
028@InterfaceAudience.Public
029public class Pair<T1, T2> implements Serializable {
030  private static final long serialVersionUID = -3986244606585552569L;
031  protected T1 first = null;
032  protected T2 second = null;
033
034  /**
035   * Default constructor.
036   */
037  public Pair() {
038  }
039
040  /**
041   * Constructor
042   * @param a operand
043   * @param b operand
044   */
045  public Pair(T1 a, T2 b) {
046    this.first = a;
047    this.second = b;
048  }
049
050  /**
051   * Constructs a new pair, inferring the type via the passed arguments
052   * @param <T1> type for first
053   * @param <T2> type for second
054   * @param a    first element
055   * @param b    second element
056   * @return a new pair containing the passed arguments
057   */
058  public static <T1, T2> Pair<T1, T2> newPair(T1 a, T2 b) {
059    return new Pair<>(a, b);
060  }
061
062  /**
063   * Replace the first element of the pair.
064   * @param a operand
065   */
066  public void setFirst(T1 a) {
067    this.first = a;
068  }
069
070  /**
071   * Replace the second element of the pair.
072   * @param b operand
073   */
074  public void setSecond(T2 b) {
075    this.second = b;
076  }
077
078  /**
079   * Return the first element stored in the pair.
080   */
081  public T1 getFirst() {
082    return first;
083  }
084
085  /**
086   * Return the second element stored in the pair.
087   */
088  public T2 getSecond() {
089    return second;
090  }
091
092  private static boolean equals(Object x, Object y) {
093    return (x == null && y == null) || (x != null && x.equals(y));
094  }
095
096  @Override
097  @SuppressWarnings("unchecked")
098  public boolean equals(Object other) {
099    return other instanceof Pair && equals(first, ((Pair) other).first)
100      && equals(second, ((Pair) other).second);
101  }
102
103  @Override
104  public int hashCode() {
105    if (first == null) return (second == null) ? 0 : second.hashCode() + 1;
106    else if (second == null) return first.hashCode() + 2;
107    else return first.hashCode() * 17 + second.hashCode();
108  }
109
110  @Override
111  public String toString() {
112    return "{" + getFirst() + "," + getSecond() + "}";
113  }
114}