The method log2(BigInteger x, RoundingMode mode) of Guava’s BigIntegerMath class returns the base-2 logarithm of x, rounded according to the specified rounding mode.
Syntax:
public static int log2(BigInteger x, RoundingMode mode)
Parameters: This method takes the following parameters:
- x: The BigInteger number whose log is to be found.
- mode: The rounding mode for calculating the log of 2.
Return Value: This method returns the base-2 logarithm of x, rounded according to the specified rounding mode.
Exceptions: This method throws the following exceptions:
- IllegalArgumentException: if x <= 0.
- ArithmeticException: if mode is RoundingMode.UNNECESSARY and x is not a power of 2.
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 illustrates the BigIntegerMath.log2() method:
Example 1:
// Java code to show implementation of// log2(BigInteger x, RoundingMode mode) method// of Guava's BigIntegerMath class import java.math.*;import com.google.common.math.BigIntegerMath; class GFG { // Driver code public static void main(String args[]) { BigInteger a1 = BigInteger.valueOf(1024); // Using log2(BigInteger x, RoundingMode mode) // method of Guava's BigIntegerMath 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("Log base 2 of " + a1 + " with rounding mode HALF_EVEN = " + BigIntegerMath .log2(a1, RoundingMode.HALF_EVEN)); BigInteger a2 = BigInteger.valueOf(15); // Using log2(BigInteger x, RoundingMode mode) // method of Guava's BigIntegerMath class // The RoundingMode HALF_DOWN rounds towards // "nearest neighbor" unless both neighbors // are equidistant, in which case round down. System.out.println("Log base 2 of " + a2 + " with rounding mode HALF_DOWN = " + BigIntegerMath .log10(a2, RoundingMode.HALF_DOWN)); }} |
Output:
Log base 2 of 1024 with rounding mode HALF_EVEN = 10 Log base 2 of 15 with rounding mode HALF_DOWN = 1
Example 2: To show IllegalArgumentException
// Java code to show implementation of// log2(BigInteger x, RoundingMode mode) method// of Guava's BigIntegerMath class import java.math.*;import com.google.common.math.BigIntegerMath; class GFG { // Driver code public static void main(String args[]) { try { BigInteger a1 = BigInteger.valueOf(-5); // Using log2(BigInteger x, RoundingMode mode) // method of Guava's BigIntegerMath 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 a1 <= 0 System.out.println("Log base 2 of " + a1 + " with rounding mode HALF_EVEN = " + BigIntegerMath .log2(a1, RoundingMode.HALF_EVEN)); } catch (Exception e) { System.out.println("Exception: " + e); } }} |
Output:
Exception: java.lang.IllegalArgumentException: x (-5) must be > 0
