public static double log(double a)

a : User input

This method returns the value ln a.

// Java program to demonstrate working
// of java.lang.Math.log() method
import java.lang.Math;
  
class Gfg {
      
    // driver code
    public static void main(String args[])
    {
  
        double a = -2.55;
        double b = 1.0 / 0;
        double c = 0, d = 145.256;
          
  
        // negative integer as argument, output NAN
        System.out.println(Math.log(a));
  
        // positive infinity as argument, output Infinity
        System.out.println(Math.log(b));
  
        // positive zero as argument, output -Infinity
        System.out.println(Math.log(c));
          
        // positive double as argument
        System.out.println(Math.log(d));
          
    }
}

NaN
Infinity
-Infinity
4.978497702968366