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Java example source code file (PairTest.java)

This example Java source code file (PairTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

double, float, integer, myinteger, object, override, pair, pairtest, test

The PairTest.java Java example source code

/*
 * 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.commons.math3.util;

import org.junit.Assert;
import org.junit.Test;

/**
 * Test for {@link Pair}.
 */
public class PairTest {

    @Test
    public void testAccessor() {
        final Pair<Integer, Double> p
            = new Pair<Integer, Double>(new Integer(1), new Double(2));
        Assert.assertEquals(new Integer(1), p.getKey());
        Assert.assertEquals(2, p.getValue().doubleValue(), Math.ulp(1d));
    }

    @Test
    public void testAccessor2() {
        final Pair<Integer, Double> p
            = new Pair<Integer, Double>(new Integer(1), new Double(2));

        // Check that both APIs refer to the same data.

        Assert.assertTrue(p.getFirst() == p.getKey());
        Assert.assertTrue(p.getSecond() == p.getValue());
    }

    @Test
    public void testEquals() {
        Pair<Integer, Double> p1 = new Pair(null, null);
        Assert.assertFalse(p1.equals(null));

        Pair<Integer, Double> p2 = new Pair(null, null);
        Assert.assertTrue(p1.equals(p2));

        p1 = new Pair<Integer, Double>(new Integer(1), new Double(2));
        Assert.assertFalse(p1.equals(p2));

        p2 = new Pair<Integer, Double>(new Integer(1), new Double(2));
        Assert.assertTrue(p1.equals(p2));

        Pair<Integer, Float> p3 = new Pair(new Integer(1), new Float(2));
        Assert.assertFalse(p1.equals(p3));
    }

    @Test
    public void testHashCode() {
        final MyInteger m1 = new MyInteger(1);
        final MyInteger m2 = new MyInteger(1);

        final Pair<MyInteger, MyInteger> p1 = new Pair(m1, m1);
        final Pair<MyInteger, MyInteger> p2 = new Pair(m2, m2);
        // Same contents, same hash code.
        Assert.assertTrue(p1.hashCode() == p2.hashCode());

        // Different contents, different hash codes.
        m2.set(2);
        Assert.assertFalse(p1.hashCode() == p2.hashCode());
    }

    @Test
    public void testToString() {
        Assert.assertEquals("[null, null]", new Pair<Object, Object>(null, null).toString());
        Assert.assertEquals("[foo, 3]", new Pair<String, Integer>("foo", 3).toString());
    }

    @Test
    public void testCreate() {
        final Pair<String, Integer> p1 = Pair.create("foo", 3);
        Assert.assertNotNull(p1);
        final Pair<String, Integer> p2 = new Pair("foo", 3);
        Assert.assertEquals(p2, p1);
    }

    /**
     * A mutable integer.
     */
    private static class MyInteger {
        private int i;

        public MyInteger(int i) {
            this.i = i;
        }

        public void set(int i) {
            this.i = i;
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof MyInteger)) {
                return false;
            } else {
                return i == ((MyInteger) o).i;
            }
        }

        @Override
        public int hashCode() {
            return i;
        }
    }
}

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