guava/guava-gwt/test-super/com/google/common/math/super/com/google/common/math/IntMathTest.java - toolchain/jack - Git at Google

 /*
  * Copyright (C) 2011 The Guava Authors
  *
  * 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.
  */

 package com.google.common.math;

 import static com.google.common.math.MathTesting.ALL_INTEGER_CANDIDATES;
 import static com.google.common.math.MathTesting.ALL_ROUNDING_MODES;
 import static com.google.common.math.MathTesting.ALL_SAFE_ROUNDING_MODES;
 import static com.google.common.math.MathTesting.EXPONENTS;
 import static com.google.common.math.MathTesting.NEGATIVE_INTEGER_CANDIDATES;
 import static com.google.common.math.MathTesting.NONZERO_INTEGER_CANDIDATES;
 import static com.google.common.math.MathTesting.POSITIVE_INTEGER_CANDIDATES;
 import static com.google.common.math.TestPlatform.intsCanGoOutOfRange;
 import static java.math.BigInteger.valueOf;
 import static java.math.RoundingMode.UNNECESSARY;

 import com.google.common.annotations.GwtCompatible;

 import junit.framework.TestCase;

 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.math.RoundingMode;

 /**
  * Tests for {@link IntMath}.
  *
  * @author Louis Wasserman
  */
 @GwtCompatible(emulated = true)
 public class IntMathTest extends TestCase {

   public void testLessThanBranchFree() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       for (int y : ALL_INTEGER_CANDIDATES) {
         if (LongMath.fitsInInt((long) x - y)) {
           int expected = (x < y) ? 1 : 0;
           int actual = IntMath.lessThanBranchFree(x, y);
           assertEquals(expected, actual);
         }
       }
     }
   }

   public void testLog2ZeroAlwaysThrows() {
     for (RoundingMode mode : ALL_ROUNDING_MODES) {
       try {
         IntMath.log2(0, mode);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }

   public void testLog2NegativeAlwaysThrows() {
     for (int x : NEGATIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         try {
           IntMath.log2(x, mode);
           fail("Expected IllegalArgumentException");
         } catch (IllegalArgumentException expected) {}
       }
     }
   }

   // Relies on the correctness of BigIntegrerMath.log2 for all modes except UNNECESSARY.
   public void testLog2MatchesBigInteger() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
         assertEquals(BigIntegerMath.log2(valueOf(x), mode), IntMath.log2(x, mode));
       }
     }
   }

   // Relies on the correctness of isPowerOfTwo(int).
   public void testLog2Exact() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       // We only expect an exception if x was not a power of 2.
       boolean isPowerOf2 = IntMath.isPowerOfTwo(x);
       try {
         assertEquals(x, 1 << IntMath.log2(x, UNNECESSARY));
         assertTrue(isPowerOf2);
       } catch (ArithmeticException e) {
         assertFalse(isPowerOf2);
       }
     }
   }

   // Relies on the correctness of BigIntegerMath.log10 for all modes except UNNECESSARY.

   // Relies on the correctness of log10(int, FLOOR) and of pow(int, int).

   // Simple test to cover sqrt(0) for all types and all modes.

   /* Relies on the correctness of BigIntegerMath.sqrt for all modes except UNNECESSARY. */

   /* Relies on the correctness of sqrt(int, FLOOR). */

   public void testDivNonZero() {
     for (int p : NONZERO_INTEGER_CANDIDATES) {
       for (int q : NONZERO_INTEGER_CANDIDATES) {
         for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
           // Skip some tests that fail due to GWT's non-compliant int implementation.
           // TODO(cpovirk): does this test fail for only some rounding modes or for all?
           if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
             continue;
           }
           int expected =
               new BigDecimal(valueOf(p)).divide(new BigDecimal(valueOf(q)), 0, mode).intValue();
           assertEquals(p + "/" + q, force32(expected), IntMath.divide(p, q, mode));
         }
       }
     }
   }

   public void testDivNonZeroExact() {
     for (int p : NONZERO_INTEGER_CANDIDATES) {
       for (int q : NONZERO_INTEGER_CANDIDATES) {
         // Skip some tests that fail due to GWT's non-compliant int implementation.
         if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
           continue;
         }
         boolean dividesEvenly = (p % q) == 0;
         try {
           assertEquals(p + "/" + q, p, IntMath.divide(p, q, UNNECESSARY) * q);
           assertTrue(p + "/" + q + " not expected to divide evenly", dividesEvenly);
         } catch (ArithmeticException e) {
           assertFalse(p + "/" + q + " expected to divide evenly", dividesEvenly);
         }
       }
     }
   }

   public void testZeroDivIsAlwaysZero() {
     for (int q : NONZERO_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         assertEquals(0, IntMath.divide(0, q, mode));
       }
     }
   }

   public void testDivByZeroAlwaysFails() {
     for (int p : ALL_INTEGER_CANDIDATES) {
       for (RoundingMode mode : ALL_ROUNDING_MODES) {
         try {
           IntMath.divide(p, 0, mode);
           fail("Expected ArithmeticException");
         } catch (ArithmeticException expected) {}
       }
     }
   }

   public void testMod() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       for (int m : POSITIVE_INTEGER_CANDIDATES) {
         assertEquals(valueOf(x).mod(valueOf(m)).intValue(), IntMath.mod(x, m));
       }
     }
   }

   public void testModNegativeModulusFails() {
     for (int x : POSITIVE_INTEGER_CANDIDATES) {
       for (int m : NEGATIVE_INTEGER_CANDIDATES) {
         try {
           IntMath.mod(x, m);
           fail("Expected ArithmeticException");
         } catch (ArithmeticException expected) {}
       }
     }
   }

   public void testModZeroModulusFails() {
     for (int x : ALL_INTEGER_CANDIDATES) {
       try {
         IntMath.mod(x, 0);
         fail("Expected ArithmeticException");
       } catch (ArithmeticException expected) {}
     }
   }

   public void testGCD() {
     for (int a : POSITIVE_INTEGER_CANDIDATES) {
       for (int b : POSITIVE_INTEGER_CANDIDATES) {
         assertEquals(valueOf(a).gcd(valueOf(b)), valueOf(IntMath.gcd(a, b)));
       }
     }
   }

   public void testGCDZero() {
     for (int a : POSITIVE_INTEGER_CANDIDATES) {
       assertEquals(a, IntMath.gcd(a, 0));
       assertEquals(a, IntMath.gcd(0, a));
     }
     assertEquals(0, IntMath.gcd(0, 0));
   }

   public void testGCDNegativePositiveThrows() {
     for (int a : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.gcd(a, 3);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
       try {
         IntMath.gcd(3, a);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }

   public void testGCDNegativeZeroThrows() {
     for (int a : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.gcd(a, 0);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
       try {
         IntMath.gcd(0, a);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }

   public void testCheckedAdd() {
     for (int a : ALL_INTEGER_CANDIDATES) {
       for (int b : ALL_INTEGER_CANDIDATES) {
         BigInteger expectedResult = valueOf(a).add(valueOf(b));
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(a + b, IntMath.checkedAdd(a, b));
           assertTrue(expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(expectedSuccess);
         }
       }
     }
   }

   public void testCheckedSubtract() {
     for (int a : ALL_INTEGER_CANDIDATES) {
       for (int b : ALL_INTEGER_CANDIDATES) {
         BigInteger expectedResult = valueOf(a).subtract(valueOf(b));
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(a - b, IntMath.checkedSubtract(a, b));
           assertTrue(expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(expectedSuccess);
         }
       }
     }
   }

   public void testCheckedMultiply() {
     for (int a : ALL_INTEGER_CANDIDATES) {
       for (int b : ALL_INTEGER_CANDIDATES) {
         BigInteger expectedResult = valueOf(a).multiply(valueOf(b));
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(a * b, IntMath.checkedMultiply(a, b));
           assertTrue(expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(expectedSuccess);
         }
       }
     }
   }

   public void testCheckedPow() {
     for (int b : ALL_INTEGER_CANDIDATES) {
       for (int k : EXPONENTS) {
         BigInteger expectedResult = valueOf(b).pow(k);
         boolean expectedSuccess = fitsInInt(expectedResult);
         try {
           assertEquals(b + "^" + k, force32(expectedResult.intValue()), IntMath.checkedPow(b, k));
           assertTrue(b + "^" + k + " should have succeeded", expectedSuccess);
         } catch (ArithmeticException e) {
           assertFalse(b + "^" + k + " should have failed", expectedSuccess);
         }
       }
     }
   }

   // Depends on the correctness of BigIntegerMath.factorial.
   public void testFactorial() {
     for (int n = 0; n <= 50; n++) {
       BigInteger expectedBig = BigIntegerMath.factorial(n);
       int expectedInt = fitsInInt(expectedBig) ? expectedBig.intValue() : Integer.MAX_VALUE;
       assertEquals(expectedInt, IntMath.factorial(n));
     }
   }

   public void testFactorialNegative() {
     for (int n : NEGATIVE_INTEGER_CANDIDATES) {
       try {
         IntMath.factorial(n);
         fail("Expected IllegalArgumentException");
       } catch (IllegalArgumentException expected) {}
     }
   }

   // Depends on the correctness of BigIntegerMath.binomial.

   /**
    * Helper method that asserts the arithmetic mean of x and y is equal
    * to the expectedMean.
    */
   private static void assertMean(int expectedMean, int x, int y) {
     assertEquals("The expectedMean should be the same as computeMeanSafely",
         expectedMean, computeMeanSafely(x, y));
     assertMean(x, y);
   }

   /**
    * Helper method that asserts the arithmetic mean of x and y is equal
    * to the result of computeMeanSafely.
    */
   private static void assertMean(int x, int y) {
     int expectedMean = computeMeanSafely(x, y);
     assertEquals(expectedMean, IntMath.mean(x, y));
     assertEquals("The mean of x and y should equal the mean of y and x",
         expectedMean, IntMath.mean(y, x));
   }

   /**
    * Computes the mean in a way that is obvious and resilient to
    * overflow by using BigInteger arithmetic.
    */
   private static int computeMeanSafely(int x, int y) {
     BigInteger bigX = BigInteger.valueOf(x);
     BigInteger bigY = BigInteger.valueOf(y);
     BigDecimal bigMean = new BigDecimal(bigX.add(bigY))
         .divide(BigDecimal.valueOf(2), BigDecimal.ROUND_FLOOR);
     // parseInt blows up on overflow as opposed to intValue() which does not.
     return Integer.parseInt(bigMean.toString());
   }

   private static boolean fitsInInt(BigInteger big) {
     return big.bitLength() <= 31;
   }

   private static int force32(int value) {
     // GWT doesn't consistently overflow values to make them 32-bit, so we need to force it.
     return value & 0xffffffff;
   }
 }
	/*
	* Copyright (C) 2011 The Guava Authors
	*
	* 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.
	*/

	package com.google.common.math;

	import static com.google.common.math.MathTesting.ALL_INTEGER_CANDIDATES;
	import static com.google.common.math.MathTesting.ALL_ROUNDING_MODES;
	import static com.google.common.math.MathTesting.ALL_SAFE_ROUNDING_MODES;
	import static com.google.common.math.MathTesting.EXPONENTS;
	import static com.google.common.math.MathTesting.NEGATIVE_INTEGER_CANDIDATES;
	import static com.google.common.math.MathTesting.NONZERO_INTEGER_CANDIDATES;
	import static com.google.common.math.MathTesting.POSITIVE_INTEGER_CANDIDATES;
	import static com.google.common.math.TestPlatform.intsCanGoOutOfRange;
	import static java.math.BigInteger.valueOf;
	import static java.math.RoundingMode.UNNECESSARY;

	import com.google.common.annotations.GwtCompatible;

	import junit.framework.TestCase;

	import java.math.BigDecimal;
	import java.math.BigInteger;
	import java.math.RoundingMode;

	/**
	* Tests for {@link IntMath}.
	*
	* @author Louis Wasserman
	*/
	@GwtCompatible(emulated = true)
	public class IntMathTest extends TestCase {

	public void testLessThanBranchFree() {
	for (int x : ALL_INTEGER_CANDIDATES) {
	for (int y : ALL_INTEGER_CANDIDATES) {
	if (LongMath.fitsInInt((long) x - y)) {
	int expected = (x < y) ? 1 : 0;
	int actual = IntMath.lessThanBranchFree(x, y);
	assertEquals(expected, actual);
	}
	}
	}
	}

	public void testLog2ZeroAlwaysThrows() {
	for (RoundingMode mode : ALL_ROUNDING_MODES) {
	try {
	IntMath.log2(0, mode);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	}
	}

	public void testLog2NegativeAlwaysThrows() {
	for (int x : NEGATIVE_INTEGER_CANDIDATES) {
	for (RoundingMode mode : ALL_ROUNDING_MODES) {
	try {
	IntMath.log2(x, mode);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	}
	}
	}

	// Relies on the correctness of BigIntegrerMath.log2 for all modes except UNNECESSARY.
	public void testLog2MatchesBigInteger() {
	for (int x : POSITIVE_INTEGER_CANDIDATES) {
	for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
	assertEquals(BigIntegerMath.log2(valueOf(x), mode), IntMath.log2(x, mode));
	}
	}
	}

	// Relies on the correctness of isPowerOfTwo(int).
	public void testLog2Exact() {
	for (int x : POSITIVE_INTEGER_CANDIDATES) {
	// We only expect an exception if x was not a power of 2.
	boolean isPowerOf2 = IntMath.isPowerOfTwo(x);
	try {
	assertEquals(x, 1 << IntMath.log2(x, UNNECESSARY));
	assertTrue(isPowerOf2);
	} catch (ArithmeticException e) {
	assertFalse(isPowerOf2);
	}
	}
	}

	// Relies on the correctness of BigIntegerMath.log10 for all modes except UNNECESSARY.

	// Relies on the correctness of log10(int, FLOOR) and of pow(int, int).

	// Simple test to cover sqrt(0) for all types and all modes.

	/* Relies on the correctness of BigIntegerMath.sqrt for all modes except UNNECESSARY. */

	/* Relies on the correctness of sqrt(int, FLOOR). */

	public void testDivNonZero() {
	for (int p : NONZERO_INTEGER_CANDIDATES) {
	for (int q : NONZERO_INTEGER_CANDIDATES) {
	for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
	// Skip some tests that fail due to GWT's non-compliant int implementation.
	// TODO(cpovirk): does this test fail for only some rounding modes or for all?
	if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
	continue;
	}
	int expected =
	new BigDecimal(valueOf(p)).divide(new BigDecimal(valueOf(q)), 0, mode).intValue();
	assertEquals(p + "/" + q, force32(expected), IntMath.divide(p, q, mode));
	}
	}
	}
	}

	public void testDivNonZeroExact() {
	for (int p : NONZERO_INTEGER_CANDIDATES) {
	for (int q : NONZERO_INTEGER_CANDIDATES) {
	// Skip some tests that fail due to GWT's non-compliant int implementation.
	if (p == -2147483648 && q == -1 && intsCanGoOutOfRange()) {
	continue;
	}
	boolean dividesEvenly = (p % q) == 0;
	try {
	assertEquals(p + "/" + q, p, IntMath.divide(p, q, UNNECESSARY) * q);
	assertTrue(p + "/" + q + " not expected to divide evenly", dividesEvenly);
	} catch (ArithmeticException e) {
	assertFalse(p + "/" + q + " expected to divide evenly", dividesEvenly);
	}
	}
	}
	}

	public void testZeroDivIsAlwaysZero() {
	for (int q : NONZERO_INTEGER_CANDIDATES) {
	for (RoundingMode mode : ALL_ROUNDING_MODES) {
	assertEquals(0, IntMath.divide(0, q, mode));
	}
	}
	}

	public void testDivByZeroAlwaysFails() {
	for (int p : ALL_INTEGER_CANDIDATES) {
	for (RoundingMode mode : ALL_ROUNDING_MODES) {
	try {
	IntMath.divide(p, 0, mode);
	fail("Expected ArithmeticException");
	} catch (ArithmeticException expected) {}
	}
	}
	}

	public void testMod() {
	for (int x : ALL_INTEGER_CANDIDATES) {
	for (int m : POSITIVE_INTEGER_CANDIDATES) {
	assertEquals(valueOf(x).mod(valueOf(m)).intValue(), IntMath.mod(x, m));
	}
	}
	}

	public void testModNegativeModulusFails() {
	for (int x : POSITIVE_INTEGER_CANDIDATES) {
	for (int m : NEGATIVE_INTEGER_CANDIDATES) {
	try {
	IntMath.mod(x, m);
	fail("Expected ArithmeticException");
	} catch (ArithmeticException expected) {}
	}
	}
	}

	public void testModZeroModulusFails() {
	for (int x : ALL_INTEGER_CANDIDATES) {
	try {
	IntMath.mod(x, 0);
	fail("Expected ArithmeticException");
	} catch (ArithmeticException expected) {}
	}
	}

	public void testGCD() {
	for (int a : POSITIVE_INTEGER_CANDIDATES) {
	for (int b : POSITIVE_INTEGER_CANDIDATES) {
	assertEquals(valueOf(a).gcd(valueOf(b)), valueOf(IntMath.gcd(a, b)));
	}
	}
	}

	public void testGCDZero() {
	for (int a : POSITIVE_INTEGER_CANDIDATES) {
	assertEquals(a, IntMath.gcd(a, 0));
	assertEquals(a, IntMath.gcd(0, a));
	}
	assertEquals(0, IntMath.gcd(0, 0));
	}

	public void testGCDNegativePositiveThrows() {
	for (int a : NEGATIVE_INTEGER_CANDIDATES) {
	try {
	IntMath.gcd(a, 3);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	try {
	IntMath.gcd(3, a);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	}
	}

	public void testGCDNegativeZeroThrows() {
	for (int a : NEGATIVE_INTEGER_CANDIDATES) {
	try {
	IntMath.gcd(a, 0);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	try {
	IntMath.gcd(0, a);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	}
	}

	public void testCheckedAdd() {
	for (int a : ALL_INTEGER_CANDIDATES) {
	for (int b : ALL_INTEGER_CANDIDATES) {
	BigInteger expectedResult = valueOf(a).add(valueOf(b));
	boolean expectedSuccess = fitsInInt(expectedResult);
	try {
	assertEquals(a + b, IntMath.checkedAdd(a, b));
	assertTrue(expectedSuccess);
	} catch (ArithmeticException e) {
	assertFalse(expectedSuccess);
	}
	}
	}
	}

	public void testCheckedSubtract() {
	for (int a : ALL_INTEGER_CANDIDATES) {
	for (int b : ALL_INTEGER_CANDIDATES) {
	BigInteger expectedResult = valueOf(a).subtract(valueOf(b));
	boolean expectedSuccess = fitsInInt(expectedResult);
	try {
	assertEquals(a - b, IntMath.checkedSubtract(a, b));
	assertTrue(expectedSuccess);
	} catch (ArithmeticException e) {
	assertFalse(expectedSuccess);
	}
	}
	}
	}

	public void testCheckedMultiply() {
	for (int a : ALL_INTEGER_CANDIDATES) {
	for (int b : ALL_INTEGER_CANDIDATES) {
	BigInteger expectedResult = valueOf(a).multiply(valueOf(b));
	boolean expectedSuccess = fitsInInt(expectedResult);
	try {
	assertEquals(a * b, IntMath.checkedMultiply(a, b));
	assertTrue(expectedSuccess);
	} catch (ArithmeticException e) {
	assertFalse(expectedSuccess);
	}
	}
	}
	}

	public void testCheckedPow() {
	for (int b : ALL_INTEGER_CANDIDATES) {
	for (int k : EXPONENTS) {
	BigInteger expectedResult = valueOf(b).pow(k);
	boolean expectedSuccess = fitsInInt(expectedResult);
	try {
	assertEquals(b + "^" + k, force32(expectedResult.intValue()), IntMath.checkedPow(b, k));
	assertTrue(b + "^" + k + " should have succeeded", expectedSuccess);
	} catch (ArithmeticException e) {
	assertFalse(b + "^" + k + " should have failed", expectedSuccess);
	}
	}
	}
	}

	// Depends on the correctness of BigIntegerMath.factorial.
	public void testFactorial() {
	for (int n = 0; n <= 50; n++) {
	BigInteger expectedBig = BigIntegerMath.factorial(n);
	int expectedInt = fitsInInt(expectedBig) ? expectedBig.intValue() : Integer.MAX_VALUE;
	assertEquals(expectedInt, IntMath.factorial(n));
	}
	}

	public void testFactorialNegative() {
	for (int n : NEGATIVE_INTEGER_CANDIDATES) {
	try {
	IntMath.factorial(n);
	fail("Expected IllegalArgumentException");
	} catch (IllegalArgumentException expected) {}
	}
	}

	// Depends on the correctness of BigIntegerMath.binomial.

	/**
	* Helper method that asserts the arithmetic mean of x and y is equal
	* to the expectedMean.
	*/
	private static void assertMean(int expectedMean, int x, int y) {
	assertEquals("The expectedMean should be the same as computeMeanSafely",
	expectedMean, computeMeanSafely(x, y));
	assertMean(x, y);
	}

	/**
	* Helper method that asserts the arithmetic mean of x and y is equal
	* to the result of computeMeanSafely.
	*/
	private static void assertMean(int x, int y) {
	int expectedMean = computeMeanSafely(x, y);
	assertEquals(expectedMean, IntMath.mean(x, y));
	assertEquals("The mean of x and y should equal the mean of y and x",
	expectedMean, IntMath.mean(y, x));
	}

	/**
	* Computes the mean in a way that is obvious and resilient to
	* overflow by using BigInteger arithmetic.
	*/
	private static int computeMeanSafely(int x, int y) {
	BigInteger bigX = BigInteger.valueOf(x);
	BigInteger bigY = BigInteger.valueOf(y);
	BigDecimal bigMean = new BigDecimal(bigX.add(bigY))
	.divide(BigDecimal.valueOf(2), BigDecimal.ROUND_FLOOR);
	// parseInt blows up on overflow as opposed to intValue() which does not.
	return Integer.parseInt(bigMean.toString());
	}

	private static boolean fitsInInt(BigInteger big) {
	return big.bitLength() <= 31;
	}

	private static int force32(int value) {
	// GWT doesn't consistently overflow values to make them 32-bit, so we need to force it.
	return value & 0xffffffff;
	}
	}