Java Guava | LongMath log10(long x, RoundingMode mode) method with Examples

The method log10(long x, RoundingMode mode) of Guava’s LongMath Class accepts two parameters and calculates the base-10 logarithmic value of the first parameter rounded according to the rounding mode specified by the second parameter.

Syntax:

public static int log10(long x, RoundingMode mode)

Parameters: The method takes 2 parameters:

• x is the long value to be found log of.
• mode is the specified rounding mode.

Return Value: This method returns Base-10 logarithm of x, rounded according to the specified rounding mode.

Exceptions: This method throws following parameters:

• IllegalArgumentException: if the value x is 0 or a negative value.
• ArithmeticException: if mode is RoundingMode.UNNECESSARY and x is not a power of ten.

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 given are some examples to understand the implementation in a better way:

Example 1:

// Java code to show implementation of
// log10(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 a1 = 10000;

        // Using log10(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.log10(
                a1,
                RoundingMode.HALF_EVEN));

        long a2 = 15;

        // Using log10(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.log10(a2,
                           RoundingMode.HALF_DOWN));
    }
}

Output :

4
1

Example 2 :

// Java code to show implementation of
// log10(long x, RoundingMode mode) method
// of Guava's LongMath class

import java.math.RoundingMode;
import com.google.common.math.LongMath;

class GFG {

    static int findlog10(long x, RoundingMode mode)
    {
        try {
            // Using log10(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
            int ans = LongMath.log10(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
            findlog10(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#log10-long-java.math.RoundingMode-