Java Guava | log2(long x, RoundingMode mode) of LongMath Class with Examples
The method log2(long x, RoundingMode mode) of Guava’s LongMath Class accepts two parameters and calculates the base-2 logarithmic value of the first parameter rounded according to the rounding mode specified by the second parameter.
Syntax:
public static int log2(long x, RoundingMode mode)
Parameters: The method takes 2 parameters, where x is a long and mode is a specified rounding mode.
Return Value: This method returns Base-2 logarithm of x, rounded according to the specified rounding mode.
Exceptions: This method throws following parameters:
- IllegalArgumentException: if x <= 0.
- ArithmeticException: if mode is RoundingMode.UNNECESSARY and x is not a power of two.
Enum RoundingMode
Enum Constant | Description |
---|---|
CEILING | Rounding mode to round towards positive infinity. |
DOWN | Rounding mode to round towards zero. |
FLOOR | Rounding mode to round towards negative infinity. |
HALF_DOWN | Rounding mode to round towards “nearest neighbor” unless both neighbors are equidistant, in which case round down. |
HALF_EVEN | Rounding mode to round towards the “nearest neighbor” unless both neighbors are equidistant, in which case, round towards the even neighbor. |
HALF_UP | Rounding mode to round towards “nearest neighbor” unless both neighbors are equidistant, in which case round up. |
UNNECESSARY | Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary. |
UP | Rounding mode to round away from zero. |
Below examples illustrate the implementation of log2() method of Guava LongMath:
Example 1 :
// Java code to show implementation of // log2(long x, RoundingMode mode) method // of Guava's LongMath class import java.math.RoundingMode; import com.google.common.math.LongMath; class GFG { // Driver code public static void main(String args[]) { long n1 = 1111 ; // Using log2(long x, RoundingMode mode) // method of Guava's LongMath class // The RoundingMode HALF_EVEN rounds towards // the "nearest neighbor" unless both neighbors // are equidistant, in which case, round towards // the even neighbor. System.out.println(LongMath.log2( n1, RoundingMode.HALF_EVEN)); long n2 = 205 ; // Using log2(long x, RoundingMode mode) // method of Guava's LongMath class // The RoundingMode HALF_DOWN rounds towards // "nearest neighbor" unless both neighbors // are equidistant, in which case round down. System.out.println(LongMath.log2( n2, RoundingMode.HALF_DOWN)); } } |
Output:
10 8
Example 2:
// Java code to show implementation of // log2(long x, RoundingMode mode) method // of Guava's LongMath class import java.math.RoundingMode; import com.google.common.math.LongMath; class GFG { static long findlog2( long x, RoundingMode mode) { try { // Using log2(long x, RoundingMode mode) // method of Guava's LongMath class // The RoundingMode HALF_EVEN rounds towards // the "nearest neighbor" unless both neighbors // are equidistant, in which case, round towards // the even neighbor. // This should throw "IllegalArgumentException" // as x <= 0 long ans = LongMath.log2(x, mode); // Return the answer return ans; } catch (Exception e) { System.out.println(e); return - 1 ; } } // Driver code public static void main(String args[]) { long x = - 122 ; try { // Function calling findlog2(x, RoundingMode.HALF_EVEN); } catch (Exception e) { System.out.println(e); } } } |
Output:
java.lang.IllegalArgumentException: x (-122) must be > 0
Reference: https://google.github.io/guava/releases/20.0/api/docs/com/google/common/math/LongMath.html#log2-long-java.math.RoundingMode-