Example 1: Java Program to calculate the method execution time

class Main{

  // create a method
  public void display(){
    System.out.println("Calculating Method execution time:");
  }

  // main method
  public static void main(String[] args){

    // create an object of the Main class
    Main obj = new Main();

    // get the start time
    long start = System.nanoTime();

    // call the method
    obj.display();

    // get the end time
    long end = System.nanoTime();

    // execution time
    long execution = end - start;
    System.out.println("Execution time: " + execution + " nanoseconds");
  }
}

Output

Calculating Method execution time:
Execution time: 656100 nanoseconds

In the above example, we have created a method named display(). The method prints a statement to the console. The program calculates the execution time of the method display().

Here, we have used the method nanoTime() of the System class. The nanoTime() method returns the current value of the running JVM in nanoseconds.

Example 2: Calculate the execution time of Recursive method

class Main{

  // create a recursive method
  public int factorial( int n ){
    if (n != 0)  // termination condition
        return n * factorial(n-1); // recursive call
    else
        return 1;
}

  // main method
  public static void main(String[] args){

    // create object of Main class
    Main obj = new Main();

    // get the start time
    long start = System.nanoTime();

    // call the method
    obj.factorial(128);

    // get the end time
    long end = System.nanoTime();

    // execution time in seconds
    long execution = (end - start);
    System.out.println("Execution time of Recursive Method is");
    System.out.println(execution + " nanoseconds");
  }
}

Output

Execution time of Recursive Method is
18600 nanoseconds

In the above example, we are calculating the execution time of recursive method named factorial().