libcore/math/src/test/java/org/apache/harmony/math/tests/java/math/BigIntegerHashCodeTest.java

/*
 *  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.
 */
/**
 * @author Elena Semukhina
 * @version $Revision$
 */

package org.apache.harmony.math.tests.java.math;

import java.math.BigInteger;

import junit.framework.TestCase;

/**
 * Class:   java.math.BigInteger
 * Method: hashCode()
 */
public class BigIntegerHashCodeTest extends TestCase {
    /**
     * Test hash codes for the same object
     */
    public void testSameObject() {
        String value1 = "12378246728727834290276457386374882976782849";
        String value2 = "-5634562095872038262928728727834290276457386374882976782849";
        BigInteger aNumber1 = new BigInteger(value1);
        BigInteger aNumber2 = new BigInteger(value2);
        int code1 = aNumber1.hashCode();
        aNumber1.add(aNumber2).shiftLeft(125);
        aNumber1.subtract(aNumber2).shiftRight(125);
        aNumber1.multiply(aNumber2).toByteArray();
        aNumber1.divide(aNumber2).bitLength();
        aNumber1.gcd(aNumber2).pow(7);
        int code2 = aNumber1.hashCode();
        assertTrue("hash codes for the same object differ", code1 == code2);
    }

    /**
     * Test hash codes for equal objects.
     */
    public void testEqualObjects() {
        String value1 = "12378246728727834290276457386374882976782849";
        String value2 = "12378246728727834290276457386374882976782849";
        BigInteger aNumber1 = new BigInteger(value1);
        BigInteger aNumber2 = new BigInteger(value2);
        int code1 = aNumber1.hashCode();
        int code2 = aNumber2.hashCode();
        if (aNumber1.equals(aNumber2)) {
            assertTrue("hash codes for equal objects are unequal", code1 == code2);
        }
    }

    /**
     * Test hash codes for unequal objects.
     * The codes are unequal.
     */
    public void testUnequalObjectsUnequal() {
        String value1 = "12378246728727834290276457386374882976782849";
        String value2 = "-5634562095872038262928728727834290276457386374882976782849";
        BigInteger aNumber1 = new BigInteger(value1);
        BigInteger aNumber2 = new BigInteger(value2);
        int code1 = aNumber1.hashCode();
        int code2 = aNumber2.hashCode();
        if (!aNumber1.equals(aNumber2)) {
            assertTrue("hash codes for unequal objects are equal", code1 != code2);
        }
    }      
}