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.util.Iterator;
021import org.apache.commons.lang3.NotImplementedException;
022import org.apache.hadoop.hbase.HConstants;
023import org.apache.yetus.audience.InterfaceAudience;
024
025/**
026 * A generic, immutable class for pairs of objects both of type <code>T</code>.
027 * @see Pair if Types differ.
028 */
029@InterfaceAudience.Public
030public class PairOfSameType<T> implements Iterable<T> {
031  private final T first;
032  private final T second;
033
034  /**
035   * Constructor
036   * @param a operand
037   * @param b operand
038   */
039  public PairOfSameType(T a, T b) {
040    this.first = a;
041    this.second = b;
042  }
043
044  /**
045   * Return the first element stored in the pair.
046   */
047  public T getFirst() {
048    return first;
049  }
050
051  /**
052   * Return the second element stored in the pair.
053   */
054  public T getSecond() {
055    return second;
056  }
057
058  private static boolean equals(Object x, Object y) {
059    return (x == null && y == null) || (x != null && x.equals(y));
060  }
061
062  @Override
063  @SuppressWarnings("unchecked")
064  public boolean equals(Object other) {
065    return other instanceof PairOfSameType && equals(first, ((PairOfSameType) other).first)
066      && equals(second, ((PairOfSameType) other).second);
067  }
068
069  @Override
070  public int hashCode() {
071    if (first == null) return (second == null) ? 0 : second.hashCode() + 1;
072    else if (second == null) return first.hashCode() + 2;
073    else return first.hashCode() * 17 + second.hashCode();
074  }
075
076  @Override
077  public String toString() {
078    return "{" + getFirst() + "," + getSecond() + "}";
079  }
080
081  @Override
082  public Iterator<T> iterator() {
083    return new Iterator<T>() {
084      private int returned = 0;
085
086      @Override
087      public boolean hasNext() {
088        return this.returned < 2;
089      }
090
091      @Override
092      public T next() {
093        if (++this.returned == 1) return getFirst();
094        else if (this.returned == 2) return getSecond();
095        else throw new IllegalAccessError("this.returned=" + this.returned);
096      }
097
098      @Override
099      public void remove() {
100        throw new NotImplementedException(HConstants.NOT_IMPLEMENTED);
101      }
102    };
103  }
104}