Program to demonstrate how to calculate natural and base 10 logarithm of a number in Java.  
Output of the program :
package com.hubberspot.code;
import java.util.Scanner;
public class LogarithmCalculation {
 public static void main(String[] args) {
  // Create a Scanner object which will read 
  // values from the console which user enters
  Scanner scanner = new Scanner(System.in);
  // Getting input from user from the console
  System.out.println("Enter value of number ");
  // Calling nextDouble method of scanner for
  // taking a double value from user and storing
  // it in number variable
  double number = scanner.nextDouble();
  System.out.println();
  System.out.println("Calculating base 10 logarithm of a number ... ");
  // In order to calculate base 10 logarithm of a number 
  // we use Math class log10() static method which takes in a 
  // number and returns back the base 10 logarithm of a number
  double result = Math.log10(number);
  // printing the result on the console
  System.out.println("Base 10 Logarithm of " + number + " is : " + result); 
  System.out.println();
  System.out.println("Calculating Natural logarithm of a number ... ");
  // In order to calculate natural logarithm of a number 
  // we use Math class log() static method which takes in a 
  // number and returns back the natural logarithm of a number
  result = Math.log(number);
  // printing the result on the console
  System.out.println("Natural Logarithm of " + number + " is : " + result); 
 }
}
Output of the program :
 

 
