Pair.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package com.sun.tools.javac.util;

import java.util.Objects;

/** A generic class for pairs.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class Pair<A, B> {

    public final A fst;
    public final B snd;

    public Pair(A fst, B snd) {
        this.fst = fst;
        this.snd = snd;
    }

    public String toString() {
        return "Pair[" + fst + "," + snd + "]";
    }

    public boolean equals(Object other) {
        return
            other instanceof Pair<?,?> &&
            Objects.equals(fst, ((Pair<?,?>)other).fst) &&
            Objects.equals(snd, ((Pair<?,?>)other).snd);
    }

    public int hashCode() {
        if (fst == null) return (snd == null) ? 0 : snd.hashCode() + 1;
        else if (snd == null) return fst.hashCode() + 2;
        else return fst.hashCode() * 17 + snd.hashCode();
    }

    public static <A,B> Pair<A,B> of(A a, B b) {
        return new Pair<>(a,b);
    }
}