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Java example source code file (LongMathTest.java)

This example Java source code file (LongMathTest.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

all_long_candidates, all_rounding_modes, androidincompatible, arithmeticexception, biginteger, expected, floor, gwtincompatible, illegalargumentexception, math, negative_long_candidates, positive_long_candidates, roundingmode, todo, unnecessary, util

The LongMathTest.java Java example source code

/*
 * 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_LONG_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.NEGATIVE_LONG_CANDIDATES;
import static com.google.common.math.MathTesting.NONZERO_LONG_CANDIDATES;
import static com.google.common.math.MathTesting.POSITIVE_INTEGER_CANDIDATES;
import static com.google.common.math.MathTesting.POSITIVE_LONG_CANDIDATES;
import static java.math.BigInteger.valueOf;
import static java.math.RoundingMode.FLOOR;
import static java.math.RoundingMode.UNNECESSARY;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.testing.NullPointerTester;

import junit.framework.TestCase;

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

/**
 * Tests for LongMath.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(emulated = true)
public class LongMathTest extends TestCase {
  public void testMaxSignedPowerOfTwo() {
    assertTrue(LongMath.isPowerOfTwo(LongMath.MAX_SIGNED_POWER_OF_TWO));
    assertFalse(LongMath.isPowerOfTwo(LongMath.MAX_SIGNED_POWER_OF_TWO * 2));
  }

  public void testCeilingPowerOfTwo() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      BigInteger expectedResult = BigIntegerMath.ceilingPowerOfTwo(BigInteger.valueOf(x));
      if (fitsInLong(expectedResult)) {
        assertEquals(expectedResult.longValue(), LongMath.ceilingPowerOfTwo(x));
      } else {
        try {
          LongMath.ceilingPowerOfTwo(x);
          fail("Expected ArithmeticException");
        } catch (ArithmeticException expected) {
        }
      }
    }
  }

  public void testFloorPowerOfTwo() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      BigInteger expectedResult = BigIntegerMath.floorPowerOfTwo(BigInteger.valueOf(x));
      assertEquals(expectedResult.longValue(), LongMath.floorPowerOfTwo(x));
    }
  }

  public void testCeilingPowerOfTwoNegative() {
    for (long x : NEGATIVE_LONG_CANDIDATES) {
      try {
        LongMath.ceilingPowerOfTwo(x);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {
      }
    }
  }

  public void testFloorPowerOfTwoNegative() {
    for (long x : NEGATIVE_LONG_CANDIDATES) {
      try {
        LongMath.floorPowerOfTwo(x);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {
      }
    }
  }

  public void testCeilingPowerOfTwoZero() {
    try {
      LongMath.ceilingPowerOfTwo(0L);
      fail("Expected IllegalArgumentException");
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testFloorPowerOfTwoZero() {
    try {
      LongMath.floorPowerOfTwo(0L);
      fail("Expected IllegalArgumentException");
    } catch (IllegalArgumentException expected) {
    }
  }

  @GwtIncompatible // TODO
  public void testConstantMaxPowerOfSqrt2Unsigned() {
    assertEquals(BigIntegerMath.sqrt(BigInteger.ZERO.setBit(2 * Long.SIZE - 1), FLOOR).longValue(),
        LongMath.MAX_POWER_OF_SQRT2_UNSIGNED);
  }

  @GwtIncompatible // BigIntegerMath // TODO(cpovirk): GWT-enable BigIntegerMath
  public void testMaxLog10ForLeadingZeros() {
    for (int i = 0; i < Long.SIZE; i++) {
      assertEquals(
          BigIntegerMath.log10(BigInteger.ONE.shiftLeft(Long.SIZE - i), FLOOR),
          LongMath.maxLog10ForLeadingZeros[i]);
    }
  }

  @GwtIncompatible // TODO
  public void testConstantsPowersOf10() {
    for (int i = 0; i < LongMath.powersOf10.length; i++) {
      assertEquals(LongMath.checkedPow(10, i), LongMath.powersOf10[i]);
    }
    try {
      LongMath.checkedPow(10, LongMath.powersOf10.length);
      fail("Expected ArithmeticException");
    } catch (ArithmeticException expected) {}
  }

  @GwtIncompatible // TODO
  public void testConstantsHalfPowersOf10() {
    for (int i = 0; i < LongMath.halfPowersOf10.length; i++) {
      assertEquals(BigIntegerMath.sqrt(BigInteger.TEN.pow(2 * i + 1), FLOOR),
          BigInteger.valueOf(LongMath.halfPowersOf10[i]));
    }
    BigInteger nextBigger =
        BigIntegerMath.sqrt(BigInteger.TEN.pow(2 * LongMath.halfPowersOf10.length + 1), FLOOR);
    assertTrue(nextBigger.compareTo(BigInteger.valueOf(Long.MAX_VALUE)) > 0);
  }

  @GwtIncompatible // TODO
  public void testConstantsSqrtMaxLong() {
    assertEquals(LongMath.sqrt(Long.MAX_VALUE, FLOOR), LongMath.FLOOR_SQRT_MAX_LONG);
  }

  @GwtIncompatible // TODO
  public void testConstantsFactorials() {
    long expected = 1;
    for (int i = 0; i < LongMath.factorials.length; i++, expected *= i) {
      assertEquals(expected, LongMath.factorials[i]);
    }
    try {
      LongMath.checkedMultiply(
          LongMath.factorials[LongMath.factorials.length - 1], LongMath.factorials.length);
      fail("Expected ArithmeticException");
    } catch (ArithmeticException expect) {}
  }

  @GwtIncompatible // TODO
  public void testConstantsBiggestBinomials() {
    for (int k = 0; k < LongMath.biggestBinomials.length; k++) {
      assertTrue(fitsInLong(BigIntegerMath.binomial(LongMath.biggestBinomials[k], k)));
      assertTrue(LongMath.biggestBinomials[k] == Integer.MAX_VALUE
          || !fitsInLong(BigIntegerMath.binomial(LongMath.biggestBinomials[k] + 1, k)));
      // In the first case, any long is valid; in the second, we want to test that the next-bigger
      // long overflows.
    }
    int k = LongMath.biggestBinomials.length;
    assertFalse(fitsInLong(BigIntegerMath.binomial(2 * k, k)));
    // 2 * k is the smallest value for which we don't replace k with (n-k).
  }

  @GwtIncompatible // TODO
  public void testConstantsBiggestSimpleBinomials() {
    for (int k = 0; k < LongMath.biggestSimpleBinomials.length; k++) {
      assertTrue(LongMath.biggestSimpleBinomials[k] <= LongMath.biggestBinomials[k]);
      long unused = simpleBinomial(LongMath.biggestSimpleBinomials[k], k); // mustn't throw
      if (LongMath.biggestSimpleBinomials[k] < Integer.MAX_VALUE) {
        // unless all n are fair game with this k
        try {
          simpleBinomial(LongMath.biggestSimpleBinomials[k] + 1, k);
          fail("Expected ArithmeticException");
        } catch (ArithmeticException expected) {}
      }
    }
    try {
      int k = LongMath.biggestSimpleBinomials.length;
      simpleBinomial(2 * k, k);
      // 2 * k is the smallest value for which we don't replace k with (n-k).
      fail("Expected ArithmeticException");
    } catch (ArithmeticException expected) {}
  }

  @AndroidIncompatible // slow
  public void testLessThanBranchFree() {
    for (long x : ALL_LONG_CANDIDATES) {
      for (long y : ALL_LONG_CANDIDATES) {
        BigInteger difference = BigInteger.valueOf(x).subtract(BigInteger.valueOf(y));
        if (fitsInLong(difference)) {
          int expected = (x < y) ? 1 : 0;
          int actual = LongMath.lessThanBranchFree(x, y);
          assertEquals(expected, actual);
        }
      }
    }
  }

  // Throws an ArithmeticException if "the simple implementation" of binomial coefficients overflows
  @GwtIncompatible // TODO
  private long simpleBinomial(int n, int k) {
    long accum = 1;
    for (int i = 0; i < k; i++) {
      accum = LongMath.checkedMultiply(accum, n - i);
      accum /= i + 1;
    }
    return accum;
  }

  @GwtIncompatible // java.math.BigInteger
  public void testIsPowerOfTwo() {
    for (long x : ALL_LONG_CANDIDATES) {
      // Checks for a single bit set.
      BigInteger bigX = BigInteger.valueOf(x);
      boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
      assertEquals(expected, LongMath.isPowerOfTwo(x));
    }
  }

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

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

  /* Relies on the correctness of BigIntegerMath.log2 for all modes except UNNECESSARY. */
  public void testLog2MatchesBigInteger() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
        // The BigInteger implementation is tested separately, use it as the reference.
        assertEquals(BigIntegerMath.log2(valueOf(x), mode), LongMath.log2(x, mode));
      }
    }
  }

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

  @GwtIncompatible // TODO
  public void testLog10ZeroAlwaysThrows() {
    for (RoundingMode mode : ALL_ROUNDING_MODES) {
      try {
        LongMath.log10(0L, mode);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
    }
  }

  @GwtIncompatible // TODO
  public void testLog10NegativeAlwaysThrows() {
    for (long x : NEGATIVE_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_ROUNDING_MODES) {
        try {
          LongMath.log10(x, mode);
          fail("Expected IllegalArgumentException");
        } catch (IllegalArgumentException expected) {}
      }
    }
  }

  // Relies on the correctness of BigIntegerMath.log10 for all modes except UNNECESSARY.
  @GwtIncompatible // TODO
  public void testLog10MatchesBigInteger() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
        assertEquals(BigIntegerMath.log10(valueOf(x), mode), LongMath.log10(x, mode));
      }
    }
  }

  // Relies on the correctness of log10(long, FLOOR) and of pow(long, int).
  @GwtIncompatible // TODO
  public void testLog10Exact() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      int floor = LongMath.log10(x, FLOOR);
      boolean expectedSuccess = LongMath.pow(10, floor) == x;
      try {
        assertEquals(floor, LongMath.log10(x, UNNECESSARY));
        assertTrue(expectedSuccess);
      } catch (ArithmeticException e) {
        if (expectedSuccess) {
          failFormat("expected log10(%s, UNNECESSARY) = %s; got ArithmeticException", x, floor);
        }
      }
    }
  }

  @GwtIncompatible // TODO
  public void testLog10TrivialOnPowerOf10() {
    long x = 1000000000000L;
    for (RoundingMode mode : ALL_ROUNDING_MODES) {
      assertEquals(12, LongMath.log10(x, mode));
    }
  }

  @GwtIncompatible // TODO
  public void testSqrtNegativeAlwaysThrows() {
    for (long x : NEGATIVE_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_ROUNDING_MODES) {
        try {
          LongMath.sqrt(x, mode);
          fail("Expected IllegalArgumentException");
        } catch (IllegalArgumentException expected) {}
      }
    }
  }

  // Relies on the correctness of BigIntegerMath.sqrt for all modes except UNNECESSARY.
  @GwtIncompatible // TODO
  public void testSqrtMatchesBigInteger() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
        // Promote the long value (rather than using longValue() on the expected value) to avoid
        // any risk of truncation which could lead to a false positive.
        assertEquals(BigIntegerMath.sqrt(valueOf(x), mode), valueOf(LongMath.sqrt(x, mode)));
      }
    }
  }

  /* Relies on the correctness of sqrt(long, FLOOR). */
  @GwtIncompatible // TODO
  public void testSqrtExactMatchesFloorOrThrows() {
    for (long x : POSITIVE_LONG_CANDIDATES) {
      long sqrtFloor = LongMath.sqrt(x, FLOOR);
      // We only expect an exception if x was not a perfect square.
      boolean isPerfectSquare = (sqrtFloor * sqrtFloor == x);
      try {
        assertEquals(sqrtFloor, LongMath.sqrt(x, UNNECESSARY));
        assertTrue(isPerfectSquare);
      } catch (ArithmeticException e) {
        assertFalse(isPerfectSquare);
      }
    }
  }

  @GwtIncompatible // TODO
  public void testPow() {
    for (long i : ALL_LONG_CANDIDATES) {
      for (int exp : EXPONENTS) {
        assertEquals(LongMath.pow(i, exp), valueOf(i)
            .pow(exp)
            .longValue());
      }
    }
  }

  @GwtIncompatible // TODO
  @AndroidIncompatible // TODO(cpovirk): File BigDecimal.divide() rounding bug.
  public void testDivNonZero() {
    for (long p : NONZERO_LONG_CANDIDATES) {
      for (long q : NONZERO_LONG_CANDIDATES) {
        for (RoundingMode mode : ALL_SAFE_ROUNDING_MODES) {
          long expected =
              new BigDecimal(valueOf(p)).divide(new BigDecimal(valueOf(q)), 0, mode).longValue();
          long actual = LongMath.divide(p, q, mode);
          if (expected != actual) {
            failFormat("expected divide(%s, %s, %s) = %s; got %s", p, q, mode, expected, actual);
          }
        }
      }
    }
  }

  @GwtIncompatible // TODO
  @AndroidIncompatible // Bug in older versions of Android we test against, since fixed.
  public void testDivNonZeroExact() {
    for (long p : NONZERO_LONG_CANDIDATES) {
      for (long q : NONZERO_LONG_CANDIDATES) {
        boolean expectedSuccess = (p % q) == 0L;

        try {
          assertEquals(p, LongMath.divide(p, q, UNNECESSARY) * q);
          assertTrue(expectedSuccess);
        } catch (ArithmeticException e) {
          if (expectedSuccess) {
            failFormat(
                "expected divide(%s, %s, UNNECESSARY) to succeed; got ArithmeticException", p, q);
          }
        }
      }
    }
  }

  @GwtIncompatible // TODO
  public void testZeroDivIsAlwaysZero() {
    for (long q : NONZERO_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_ROUNDING_MODES) {
        assertEquals(0L, LongMath.divide(0L, q, mode));
      }
    }
  }

  @GwtIncompatible // TODO
  public void testDivByZeroAlwaysFails() {
    for (long p : ALL_LONG_CANDIDATES) {
      for (RoundingMode mode : ALL_ROUNDING_MODES) {
        try {
          LongMath.divide(p, 0L, mode);
          fail("Expected ArithmeticException");
        } catch (ArithmeticException expected) {}
      }
    }
  }

  @GwtIncompatible // TODO
  public void testIntMod() {
    for (long x : ALL_LONG_CANDIDATES) {
      for (int m : POSITIVE_INTEGER_CANDIDATES) {
        assertEquals(valueOf(x)
            .mod(valueOf(m))
            .intValue(), LongMath.mod(x, m));
      }
    }
  }

  @GwtIncompatible // TODO
  public void testIntModNegativeModulusFails() {
    for (long x : ALL_LONG_CANDIDATES) {
      for (int m : NEGATIVE_INTEGER_CANDIDATES) {
        try {
          LongMath.mod(x, m);
          fail("Expected ArithmeticException");
        } catch (ArithmeticException expected) {}
      }
    }
  }

  @GwtIncompatible // TODO
  public void testIntModZeroModulusFails() {
    for (long x : ALL_LONG_CANDIDATES) {
      try {
        LongMath.mod(x, 0);
        fail("Expected AE");
      } catch (ArithmeticException expected) {}
    }
  }

  @AndroidIncompatible // slow
  @GwtIncompatible // TODO
  public void testMod() {
    for (long x : ALL_LONG_CANDIDATES) {
      for (long m : POSITIVE_LONG_CANDIDATES) {
        assertEquals(valueOf(x)
            .mod(valueOf(m))
            .longValue(), LongMath.mod(x, m));
      }
    }
  }

  @GwtIncompatible // TODO
  public void testModNegativeModulusFails() {
    for (long x : ALL_LONG_CANDIDATES) {
      for (long m : NEGATIVE_LONG_CANDIDATES) {
        try {
          LongMath.mod(x, m);
          fail("Expected ArithmeticException");
        } catch (ArithmeticException expected) {}
      }
    }
  }

  public void testGCDExhaustive() {
    for (long a : POSITIVE_LONG_CANDIDATES) {
      for (long b : POSITIVE_LONG_CANDIDATES) {
        assertEquals(valueOf(a).gcd(valueOf(b)), valueOf(LongMath.gcd(a, b)));
      }
    }
  }

  @GwtIncompatible // TODO
  public void testGCDZero() {
    for (long a : POSITIVE_LONG_CANDIDATES) {
      assertEquals(a, LongMath.gcd(a, 0));
      assertEquals(a, LongMath.gcd(0, a));
    }
    assertEquals(0, LongMath.gcd(0, 0));
  }

  @GwtIncompatible // TODO
  public void testGCDNegativePositiveThrows() {
    for (long a : NEGATIVE_LONG_CANDIDATES) {
      try {
        LongMath.gcd(a, 3);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
      try {
        LongMath.gcd(3, a);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
    }
  }

  @GwtIncompatible // TODO
  public void testGCDNegativeZeroThrows() {
    for (long a : NEGATIVE_LONG_CANDIDATES) {
      try {
        LongMath.gcd(a, 0);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
      try {
        LongMath.gcd(0, a);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
    }
  }

  @AndroidIncompatible // slow
  @GwtIncompatible // TODO
  public void testCheckedAdd() {
    for (long a : ALL_LONG_CANDIDATES) {
      for (long b : ALL_LONG_CANDIDATES) {
        BigInteger expectedResult = valueOf(a).add(valueOf(b));
        boolean expectedSuccess = fitsInLong(expectedResult);
        try {
          assertEquals(a + b, LongMath.checkedAdd(a, b));
          assertTrue(expectedSuccess);
        } catch (ArithmeticException e) {
          if (expectedSuccess) {
            failFormat(
                "expected checkedAdd(%s, %s) = %s; got ArithmeticException", a, b, expectedResult);
          }
        }
      }
    }
  }

  @GwtIncompatible // TODO
  @AndroidIncompatible // slow
  public void testCheckedSubtract() {
    for (long a : ALL_LONG_CANDIDATES) {
      for (long b : ALL_LONG_CANDIDATES) {
        BigInteger expectedResult = valueOf(a).subtract(valueOf(b));
        boolean expectedSuccess = fitsInLong(expectedResult);
        try {
          assertEquals(a - b, LongMath.checkedSubtract(a, b));
          assertTrue(expectedSuccess);
        } catch (ArithmeticException e) {
          if (expectedSuccess) {
            failFormat(
                "expected checkedSubtract(%s, %s) = %s; got ArithmeticException",
                a,
                b,
                expectedResult);
          }
        }
      }
    }
  }

  @GwtIncompatible // TODO
  @AndroidIncompatible // slow
  public void testCheckedMultiply() {
    boolean isAndroid = System.getProperties().getProperty("java.runtime.name").contains("Android");
    for (long a : ALL_LONG_CANDIDATES) {
      for (long b : ALL_LONG_CANDIDATES) {
        if (isAndroid && a == -4294967296L && b == 2147483648L) {
          /*
           * Bug in older versions of Android we test against, since fixed: -9223372036854775808L /
           * -4294967296L = -9223372036854775808L!
           *
           * To be clear, this bug affects not the test's computation of the expected result but the
           * _actual prod code_. But it probably affects only unusual cases.
           */
          continue;
        }
        BigInteger expectedResult = valueOf(a).multiply(valueOf(b));
        boolean expectedSuccess = fitsInLong(expectedResult);
        try {
          assertEquals(a * b, LongMath.checkedMultiply(a, b));
          assertTrue(expectedSuccess);
        } catch (ArithmeticException e) {
          if (expectedSuccess) {
            failFormat(
                "expected checkedMultiply(%s, %s) = %s; got ArithmeticException",
                a,
                b,
                expectedResult);
          }
        }
      }
    }
  }

  @GwtIncompatible // TODO
  public void testCheckedPow() {
    for (long b : ALL_LONG_CANDIDATES) {
      for (int exp : EXPONENTS) {
        BigInteger expectedResult = valueOf(b).pow(exp);
        boolean expectedSuccess = fitsInLong(expectedResult);
        try {
          assertEquals(expectedResult.longValue(), LongMath.checkedPow(b, exp));
          assertTrue(expectedSuccess);
        } catch (ArithmeticException e) {
          if (expectedSuccess) {
            failFormat(
                "expected checkedPow(%s, %s) = %s; got ArithmeticException",
                b,
                exp,
                expectedResult);
          }
        }
      }
    }
  }

  @AndroidIncompatible // slow
  @GwtIncompatible // TODO
  public void testSaturatedAdd() {
    for (long a : ALL_LONG_CANDIDATES) {
      for (long b : ALL_LONG_CANDIDATES) {
        assertOperationEquals(
            a, b, "s+", saturatedCast(valueOf(a).add(valueOf(b))), LongMath.saturatedAdd(a, b));
      }
    }
  }

  @AndroidIncompatible // slow
  @GwtIncompatible // TODO
  public void testSaturatedSubtract() {
    for (long a : ALL_LONG_CANDIDATES) {
      for (long b : ALL_LONG_CANDIDATES) {
        assertOperationEquals(
            a,
            b,
            "s-",
            saturatedCast(valueOf(a).subtract(valueOf(b))),
            LongMath.saturatedSubtract(a, b));
      }
    }
  }

  @AndroidIncompatible // slow
  @GwtIncompatible // TODO
  public void testSaturatedMultiply() {
    for (long a : ALL_LONG_CANDIDATES) {
      for (long b : ALL_LONG_CANDIDATES) {
        assertOperationEquals(
            a,
            b,
            "s*",
            saturatedCast(valueOf(a).multiply(valueOf(b))),
            LongMath.saturatedMultiply(a, b));
      }
    }
  }

  @GwtIncompatible // TODO
  public void testSaturatedPow() {
    for (long a : ALL_LONG_CANDIDATES) {
      for (int b : EXPONENTS) {
        assertOperationEquals(
            a, b, "s^", saturatedCast(valueOf(a).pow(b)), LongMath.saturatedPow(a, b));
      }
    }
  }

  private void assertOperationEquals(long a, long b, String op, long expected, long actual) {
    if (expected != actual) {
      fail("Expected for " + a + " " + op + " " + b + " = " + expected + ", but got " + actual);
    }
  }

  // Depends on the correctness of BigIntegerMath.factorial.
  @GwtIncompatible // TODO
  public void testFactorial() {
    for (int n = 0; n <= 50; n++) {
      BigInteger expectedBig = BigIntegerMath.factorial(n);
      long expectedLong = fitsInLong(expectedBig) ? expectedBig.longValue() : Long.MAX_VALUE;
      assertEquals(expectedLong, LongMath.factorial(n));
    }
  }

  @GwtIncompatible // TODO
  public void testFactorialNegative() {
    for (int n : NEGATIVE_INTEGER_CANDIDATES) {
      try {
        LongMath.factorial(n);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
    }
  }

  // Depends on the correctness of BigIntegerMath.binomial.
  public void testBinomial() {
    for (int n = 0; n <= 70; n++) {
      for (int k = 0; k <= n; k++) {
        BigInteger expectedBig = BigIntegerMath.binomial(n, k);
        long expectedLong = fitsInLong(expectedBig) ? expectedBig.longValue() : Long.MAX_VALUE;
        assertEquals(expectedLong, LongMath.binomial(n, k));
      }
    }
  }

  @GwtIncompatible // Slow
  public void testBinomial_exhaustiveNotOverflowing() {
    // Tests all of the inputs to LongMath.binomial that won't cause it to overflow, that weren't
    // tested in the previous method, for k >= 3.
    for (int k = 3; k < LongMath.biggestBinomials.length; k++) {
      for (int n = 70; n <= LongMath.biggestBinomials[k]; n++) {
        assertEquals(BigIntegerMath.binomial(n, k).longValue(), LongMath.binomial(n, k));
      }
    }
  }

  public void testBinomialOutside() {
    for (int n = 0; n <= 50; n++) {
      try {
        LongMath.binomial(n, -1);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
      try {
        LongMath.binomial(n, n + 1);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
    }
  }

  public void testBinomialNegative() {
    for (int n : NEGATIVE_INTEGER_CANDIDATES) {
      try {
        LongMath.binomial(n, 0);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {}
    }
  }

  @GwtIncompatible // far too slow
  public void testSqrtOfPerfectSquareAsDoubleIsPerfect() {
    // This takes just over a minute on my machine.
    for (long n = 0; n <= LongMath.FLOOR_SQRT_MAX_LONG; n++) {
      long actual = (long) Math.sqrt(n * n);
      assertTrue(actual == n);
    }
  }

  public void testSqrtOfLongIsAtMostFloorSqrtMaxLong() {
    long sqrtMaxLong = (long) Math.sqrt(Long.MAX_VALUE);
    assertTrue(sqrtMaxLong <= LongMath.FLOOR_SQRT_MAX_LONG);
  }

  @AndroidIncompatible // slow
  @GwtIncompatible // java.math.BigInteger
  public void testMean() {
    // Odd-sized ranges have an obvious mean
    assertMean(2, 1, 3);

    assertMean(-2, -3, -1);
    assertMean(0, -1, 1);
    assertMean(1, -1, 3);
    assertMean((1L << 62) - 1, -1, Long.MAX_VALUE);

    // Even-sized ranges should prefer the lower mean
    assertMean(2, 1, 4);
    assertMean(-3, -4, -1);
    assertMean(0, -1, 2);
    assertMean(0, Long.MIN_VALUE + 2, Long.MAX_VALUE);
    assertMean(0, 0, 1);
    assertMean(-1, -1, 0);
    assertMean(-1, Long.MIN_VALUE, Long.MAX_VALUE);

    // x == y == mean
    assertMean(1, 1, 1);
    assertMean(0, 0, 0);
    assertMean(-1, -1, -1);
    assertMean(Long.MIN_VALUE, Long.MIN_VALUE, Long.MIN_VALUE);
    assertMean(Long.MAX_VALUE, Long.MAX_VALUE, Long.MAX_VALUE);

    // Exhaustive checks
    for (long x : ALL_LONG_CANDIDATES) {
      for (long y : ALL_LONG_CANDIDATES) {
        assertMean(x, y);
      }
    }
  }

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

  /**
   * Computes the mean in a way that is obvious and resilient to
   * overflow by using BigInteger arithmetic.
   */
  private static long computeMeanSafely(long x, long 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 Long.parseLong(bigMean.toString());
  }

  private static boolean fitsInLong(BigInteger big) {
    return big.bitLength() <= 63;
  }

  private static final BigInteger MAX_LONG = BigInteger.valueOf(Long.MAX_VALUE);
  private static final BigInteger MIN_LONG = BigInteger.valueOf(Long.MIN_VALUE);

  private static long saturatedCast(BigInteger big) {
    if (big.compareTo(MAX_LONG) > 0) {
      return Long.MAX_VALUE;
    }
    if (big.compareTo(MIN_LONG) < 0) {
      return Long.MIN_VALUE;
    }
    return big.longValue();
  }

  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {
    NullPointerTester tester = new NullPointerTester();
    tester.setDefault(int.class, 1);
    tester.setDefault(long.class, 1L);
    tester.testAllPublicStaticMethods(LongMath.class);
  }

  @GwtIncompatible // isPrime is GWT-incompatible
  public void testIsPrimeSmall() {
    // Check the first 1000 integers
    for (int i = 2; i < 1000; i++) {
      assertEquals(BigInteger.valueOf(i).isProbablePrime(100), LongMath.isPrime(i));
    }
  }

  @GwtIncompatible // isPrime is GWT-incompatible
  public void testIsPrimeManyConstants() {
    // Test the thorough test inputs, which also includes special constants in the Miller-Rabin
    // tests.
    for (long l : POSITIVE_LONG_CANDIDATES) {
      assertEquals(BigInteger.valueOf(l).isProbablePrime(100), LongMath.isPrime(l));
    }
  }

  @GwtIncompatible // isPrime is GWT-incompatible
  public void testIsPrimeOnUniformRandom() {
    Random rand = new Random(1);
    for (int bits = 10; bits < 63; bits++) {
      for (int i = 0; i < 2000; i++) {
        // A random long between 0 and Long.MAX_VALUE, inclusive.
        long l = rand.nextLong() & ((1L << bits) - 1);
        assertEquals(BigInteger.valueOf(l).isProbablePrime(100), LongMath.isPrime(l));
      }
    }
  }

  @GwtIncompatible // isPrime is GWT-incompatible
  public void testIsPrimeOnRandomPrimes() {
    Random rand = new Random(1);
    for (int bits = 10; bits < 63; bits++) {
      for (int i = 0; i < 100; i++) {
        long p = BigInteger.probablePrime(bits, rand).longValue();
        assertTrue(LongMath.isPrime(p));
      }
    }
  }

  @GwtIncompatible // isPrime is GWT-incompatible
  public void testIsPrimeOnRandomComposites() {
    Random rand = new Random(1);
    for (int bits = 5; bits < 32; bits++) {
      for (int i = 0; i < 100; i++) {
        long p = BigInteger.probablePrime(bits, rand).longValue();
        long q = BigInteger.probablePrime(bits, rand).longValue();
        assertFalse(LongMath.isPrime(p * q));
      }
    }
  }

  @GwtIncompatible // isPrime is GWT-incompatible
  public void testIsPrimeThrowsOnNegative() {
    try {
      LongMath.isPrime(-1);
      fail("Expected IllegalArgumentException");
    } catch (IllegalArgumentException expected) {}
  }

  @GwtIncompatible // String.format
  private static void failFormat(String template, Object... args) {
    fail(String.format(template, args));
  }
}

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