user/test/com/google/gwt/emultest/java/math/BigIntegerHashCodeTest.java

/*
 * Copyright 2009 Google Inc.
 * 
 * Licensed 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.
 */

/*
 * 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.
 * 
 * INCLUDES MODIFICATIONS BY GOOGLE.
 */
/**
 * author Elena Semukhina
 */
package com.google.gwt.emultest.java.math;

import com.google.gwt.emultest.java.util.EmulTestBase;

import java.math.BigInteger;

/**
 * Class: java.math.BigInteger Method: hashCode().
 */
public class BigIntegerHashCodeTest extends EmulTestBase {
  /**
   * 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 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 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);
    }
  }
}