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