Pair.java

/*
 * MIT License
 *
 * Copyright (c) 2009-2016 Ignacio Calderon <https://github.com/kronenthaler>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package libai.common;

import java.util.Objects;

/**
 * Pair class allows to keep two elements of possibly different types in the
 * same structure and can be used for keep pairs key-value.
 *
 * @author kronenthaler
 */
public final class Pair<V extends Comparable<V>, K> implements Comparable<Pair<V, K>> {

    /**
     * First element of the pair (the 'key').
     */
    public V first;
    /**
     * Second element of the pair (the 'value').
     */
    public K second;

    /**
     * Constructor.
     *
     * @param x the first element for the pair.
     * @param y the second element for the pair.
     */
    public Pair(V x, K y) {
        first = x;
        second = y;
    }

    /**
     * Compare two pairs by the first element. The first element type must
     * implement the Comparable interface.
     *
     * @param o The pair to compare with.
     * @return -1 if this is less than o, 0 if are equals, 1 if this is greater
     * than o.
     */
    @Override
    public int compareTo(Pair<V, K> o) {
        return first.compareTo(o.first);
    }

    @Override
    public int hashCode() {
        return Objects.hash(first, second);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        final Pair<V, K> other = (Pair<V, K>) obj;

        return Objects.equals(first, other.first) && Objects.equals(second, other.second);
    }

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