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));
}
} |
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);
}
}
} |
java.lang.IllegalArgumentException: x (-122) must be > 0