Guava - LongMath Class

LongMath provides utility methods on long.

Class Declaration

Following is the declaration for com.google.common.math.LongMath class −

@GwtCompatible(emulated = true)
public final class LongMath
   extends Object

Methods

Sr.No	Method & Description
1	static long binomial(int n, int k) Returns n choose k, also known as the binomial coefficient of n and k, or Long.MAX_VALUE if the result does not fit in a long.
2	static long checkedAdd(long a, long b) Returns the sum of a and b, provided it does not overflow.
3	static long checkedMultiply(long a, long b) Returns the product of a and b, provided it does not overflow.
4	static long checkedPow(long b, int k) Returns the b to the kth power, provided it does not overflow.
5	static long checkedSubtract(long a, long b) Returns the difference of a and b, provided it does not overflow.
6	static long divide(long p, long q, RoundingMode mode) Returns the result of dividing p by q, rounding using the specified RoundingMode.
7	static long factorial(int n) Returns n!, that is, the product of the first n positive integers, 1 if n == 0, or Long.MAX_VALUE if the result does not fit in a long.
8	static long gcd(long a, long b) Returns the greatest common divisor of a, b.
9	static boolean isPowerOfTwo(long x) Returns true if x represents a power of two.
10	static int log10(long x, RoundingMode mode) Returns the base-10 logarithm of x, rounded according to the specified rounding mode.
11	static int log2(long x, RoundingMode mode) Returns the base-2 logarithm of x, rounded according to the specified rounding mode.
12	static long mean(long x, long y) Returns the arithmetic mean of x and y, rounded toward negative infinity.
13	static int mod(long x, int m) Returns x mod m, a non-negative value less than m.
14	static long mod(long x, long m) Returns x mod m, a non-negative value less than m.
15	static long pow(long b, int k) Returns b to the kth power.
16	static long sqrt(long x, RoundingMode mode) Returns the square root of x, rounded with the specified rounding mode.

Methods Inherited

This class inherits methods from the following class −

java.lang.Object

Example of LongMath Class

Create the following java program using any editor of your choice in say C:/> Guava.

GuavaTester.java

import java.math.RoundingMode;
import com.google.common.math.LongMath;

public class GuavaTester {

   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testLongMath();
   }

   private void testLongMath() {
      try {
         System.out.println(LongMath.checkedAdd(Long.MAX_VALUE, Long.MAX_VALUE));
         
      } catch(ArithmeticException e) {
         System.out.println("Error: " + e.getMessage());
      }

      System.out.println(LongMath.divide(100, 5, RoundingMode.UNNECESSARY));
      try {
         //exception will be thrown as 100 is not completely divisible by 3
         // thus rounding is required, and RoundingMode is set as UNNESSARY
         System.out.println(LongMath.divide(100, 3, RoundingMode.UNNECESSARY));
         
      } catch(ArithmeticException e) {
         System.out.println("Error: " + e.getMessage());
      }

      System.out.println("Log2(2): " + LongMath.log2(2, RoundingMode.HALF_EVEN));

      System.out.println("Log10(10): " + LongMath.log10(10, RoundingMode.HALF_EVEN));

      System.out.println("sqrt(100): " + LongMath.sqrt(LongMath.pow(10,2), RoundingMode.HALF_EVEN));

      System.out.println("gcd(100,50): " + LongMath.gcd(100,50));

      System.out.println("modulus(100,50): " + LongMath.mod(100,50));

      System.out.println("factorial(5): " + LongMath.factorial(5));
   }
}

Verify the Result

Compile the class using javac compiler as follows −

C:\Guava>javac GuavaTester.java

Now run the GuavaTester to see the result.

C:\Guava>java GuavaTester

See the result.

Error: overflow
20
Error: mode was UNNECESSARY, but rounding was necessary
Log2(2): 1
Log10(10): 1
sqrt(100): 10
gcd(100,50): 50
modulus(100,50): 0
factorial(5): 120

guava_math_utilities.htm