001// Copyright (c) FIRST and other WPILib contributors.
002// Open Source Software; you can modify and/or share it under the terms of
003// the WPILib BSD license file in the root directory of this project.
004
005package edu.wpi.first.math;
006
007import java.util.Objects;
008
009/**
010 * Represents a pair of two objects.
011 *
012 * @param <A> The first object's type.
013 * @param <B> The second object's type.
014 */
015public class Pair<A, B> {
016  private final A m_first;
017  private final B m_second;
018
019  /**
020   * Constructs a pair.
021   *
022   * @param first The first object.
023   * @param second The second object.
024   */
025  public Pair(A first, B second) {
026    m_first = first;
027    m_second = second;
028  }
029
030  /**
031   * Returns the first object.
032   *
033   * @return The first object.
034   */
035  public A getFirst() {
036    return m_first;
037  }
038
039  /**
040   * Returns the second object.
041   *
042   * @return The second object.
043   */
044  public B getSecond() {
045    return m_second;
046  }
047
048  /**
049   * Returns a pair comprised of the two given objects.
050   *
051   * @param <A> The first object's type.
052   * @param <B> The second object's type.
053   * @param a The first object.
054   * @param b The second object.
055   * @return A pair comprised of the two given objects.
056   */
057  public static <A, B> Pair<A, B> of(A a, B b) {
058    return new Pair<>(a, b);
059  }
060
061  @Override
062  public String toString() {
063    return String.format("Pair(%s, %s)", m_first, m_second);
064  }
065
066  /**
067   * Checks equality between this Pair and another object.
068   *
069   * @param obj The other object.
070   * @return Whether the two objects are equal or not.
071   */
072  @Override
073  public boolean equals(Object obj) {
074    return obj == this
075        || obj instanceof Pair<?, ?> other
076            && Objects.equals(m_first, other.getFirst())
077            && Objects.equals(m_second, other.getSecond());
078  }
079
080  @Override
081  public int hashCode() {
082    return Objects.hash(m_first, m_second);
083  }
084}