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This module contains non-RDF library code and the common system runtime.

There is a newer version: 5.2.0

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.atlas.lib;

import static org.apache.jena.atlas.lib.Lib.hashCodeObject;
import static org.apache.jena.atlas.lib.StrUtils.str;

import java.util.Map;
import java.util.Objects;

/** A pair */
public class Pair
{
    public static  Pair create(L x, R y) { return new Pair<>(x,y); }

    final A a;
    final B b;
    public Pair(A a, B b) { this.a = a; this.b = b; }

    public A getLeft()  { return a; }
    public B getRight() { return b; }

    public A car() { return a; }
    public B cdr() { return b; }

    /** Add to a map using the pair as key-value. */
    public static  void addToMap(Map map, Pair pair) {
        map.put(pair.getLeft(), pair.getRight());
    }

    /** Add to a map using this pair as key-value. */
    public void addToMap(Map map) {
        map.put(getLeft(), getRight());
    }

    @Override
    public int hashCode() {
        return hashCodeObject(car()) ^ hashCodeObject(cdr())<<1;
    }

    @Override
    public boolean equals(Object other){
        if ( this == other ) return true;

        // If it's a pair of a different  then .equals
        // Pair(null,null) is equal to Pair(null ,null)
        // Type erasure makes this hard to check otherwise.
        // Use class X extends Pair and implement .equals to do
        // instanceof then call super.equals.

        if ( !(other instanceof Pair p2) )
            return false;
        return Objects.equals(car(), p2.car()) && Objects.equals(cdr(), p2.cdr());
    }

    /** Test whether the arguments are equal to the elements of this pair */
    public boolean equalElts(A left, B right) {
        return Objects.equals(car(), left) && Objects.equals(cdr(), right);
    }

    @Override
    public String toString() { return "("+str(a)+", "+str(b)+")"; }
}