How to use log1p() in java programming?

This log1p() function from java.lang.Math library is used to calculate the natural logarithm (base e) of the sum specified value and 1. It is a static method so we will call this function by using the class name.

Syntax

public static double log1p(double value)

Parameters

Value whose logarithm is to be computed.

• value: an argument value of primitive double type.

Return Value

It will return the natural logarithm ln(x + 1).

Special Cases

The argument value should be of double type.

• If the argument is a positive value, it will return ln(x + 1).
• If the argument is NaN or less than -1, it will return NaN.
• If the argument is positive infinity, it will return the result as Positive Infinity.
• If the argument is a negative one, it will return Negative Infinity.
• If the argument is positive/negative zero, it will return Zero.

Explanation

The code snippet below covers all special cases mentioned above. Execute the code below and read the comments carefully to grab the whole concept.

// Load Math library
import java.lang.Math;
// Main class
public class AlgoIdeas {
	// main driver class
	public static void main(String args[])
	{
		double num1 = 23.45, 
		num2 = -145.25, 
		num3 = 1.0 / 0,
		num4 = -1,
		num5 = 0;
		// positive double value
		// output will be natural log of double type
		System.out.println(Math.log1p(num1));
		// positive zero
		// output value will be Zero
		System.out.println(Math.log1p(num5));
		// negative double value
		// output will be NAN
		System.out.println(Math.log1p(num2));
		// positive infinity
		// output will be positive infinity
		System.out.println(Math.log1p(num3));
		// -1 as an argument
		// output will be negative infinity
		System.out.println(Math.log1p(num4));
	}
}

• Line#2: Importing Math library into the program.
• Line#4: Main class to execute project code called. i.e. AlgoIdeas.
• Line#6: main() function to start program execution.
• Line# 8-12: Defining multiple variables with different values to cover each use case.
• Line#15-27: Invoking Math.log1p() to calculate natural log parallel to each use case with different values.