The log2(int x, RoundingMode mode) method of Guava’s IntMath 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(int x, RoundingMode mode)
Parameters : The method takes 2 parameters, where x is an integer 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 :
- 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 IntMath:
Example 1 :
// Java code to show implementation of// log2(int x, RoundingMode mode) method// of Guava's IntMath classimport java.math.RoundingMode;import com.google.common.math.IntMath; class GFG { // Driver code public static void main(String args[]) { int a1 = 1542; // Using log2(int x, RoundingMode mode) // method of Guava's IntMath 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(IntMath.log2(a1, RoundingMode.HALF_EVEN)); int a2 = 451; // Using log2(int x, RoundingMode mode) // method of Guava's IntMath class // The RoundingMode HALF_DOWN rounds towards // "nearest neighbor" unless both neighbors // are equidistant, in which case round down. System.out.println(IntMath.log2(a2, RoundingMode.HALF_DOWN)); }} |
Output:
11 9
Example 2 :
// Java code to show implementation of// log2(int x, RoundingMode mode) method// of Guava's IntMath classimport java.math.RoundingMode;import com.google.common.math.IntMath; class GFG { static int findlog2(int x, RoundingMode mode) { try { // Using log2(int x, RoundingMode mode) // method of Guava's IntMath 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 int ans = IntMath.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[]) { int x = -152; try { // Function calling findlog2(x, RoundingMode.HALF_EVEN); } catch (Exception e) { System.out.println(e); } }} |
Output:
java.lang.IllegalArgumentException: x (-152) must be > 0
