The java.lang.Math.log1p() is one of the Java Math Library method which is used to return the natural logarithm of the sum of the arguments and 1.For the small values, the result of log1p(a) is much closer to the true result of ln(1 + a) than the floating-point evaluation of log(1.0 + a).There are various cases :

• If the argument is positive double value, Math.log1p() method will return the logarithm of the given value.
• If the argument is NaN or less than -1, Math.log1p() method will return NaN.
• If the argument is positive infinity, Math.log1p() method will return the result as Positive Infinity
• If the argument is negative one, Math.log1p() method will return Negative Infinity
• If the argument is positive or negative zero, Math.log1p() method will return Zero

Syntax :

public static double log1p(double a)

Parameter :

a : User input

Return :

This method returns the value ln(x + 1), the natural log of x + 1.

Example :To show working of java.lang.Math.log1p() method. 

// Java program to demonstrate working
// of java.lang.Math.log1p() method
import java.lang.Math;

class Gfg {

    // driver code
    public static void main(String args[])
    {
        double a = 23.45;
        double b = -145.25;
        double c = 1.0 / 0;
        double d = -1;
        double e = 0;

         // positive double value as argument,
        // output double value
        System.out.println(Math.log1p(a));

         // negative integer as argument,
        // output NAN
        System.out.println(Math.log1p(b));

         // positive infinity as argument,
        // output Positive Infinity
        System.out.println(Math.log1p(c));

        // negative one as argument,
        // output Negative Infinity
        System.out.println(Math.log1p(d));

        // positive zero as argument,
        // output Zero
        System.out.println(Math.log1p(e));
    }
}

3.196630215920881
NaN
Infinity
-Infinity
0.0