Question

How to calculate the running time of a program in Java

Answer 1

public class MyClass {
    public static void main(String args[]) {
        long startTime = System.currentTimeMillis();
        
        // program
        long sum = 0;
        for (int i = 1; i <= 1000_000_000; i++) {
			    sum += 1;
		}	
        // program

        long endTime = System.currentTimeMillis();

        long elapsedTime = endTime - startTime;

        System.out.println("Elapsed time: " + elapsedTime + " milliseconds");
    }
}
 
 
 
 
/*
run:
      
Elapsed time: 15 milliseconds
      
*/

 

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Answer 2

import java.util.Calendar;
import java.util.Date;

public class MyClass {
     public static int getMonthFromCurrentDate() {
        Date date = new Date();
          
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
  
        return cal.get(Calendar.MONTH) + 1;
    }
    public static void test(long sum) {
        sum += 1;
    }
    public static void main(String args[]) {
        long startTime = System.currentTimeMillis();
        
        // program
        long sum = 0;
        for (int i = 1; i <= 1_000_000; i++) {
			    sum += 1;
			    sum += 2;
			    test(sum);
			    int month = getMonthFromCurrentDate();
		}	
        // program

        long endTime = System.currentTimeMillis();

        long elapsedTime = endTime - startTime;
        
        long elapsedTimeInSeconds = elapsedTime / 1000;
        long elapsedTimeInMinutes = elapsedTime / 60000;

        System.out.println(elapsedTime + " milliseconds");
        System.out.println(elapsedTimeInSeconds + " seconds");
        System.out.println(elapsedTimeInMinutes + " minutes");
    }
}
 
 
 
 
/*
run:
      
1739 milliseconds
1 seconds
0 minutes
      
*/

 

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Answer 3

import java.util.Calendar;
import java.util.Date;
import java.time.Duration;
import java.time.Instant;

public class MyClass {
     public static int getMonthFromCurrentDate() {
        Date date = new Date();
          
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
  
        return cal.get(Calendar.MONTH) + 1;
    }
    public static void test(long sum) {
        sum += 1;
    }
    public static void main(String args[]) {
        Instant start = Instant.now();
        
        // program
        long sum = 0;
        for (int i = 1; i <= 1_000_000; i++) {
			    sum += 1;
			    sum += 2;
			    test(sum);
			    int month = getMonthFromCurrentDate();
		}	
        // program

        Instant end = Instant.now();
		
		System.out.println(Duration.between(start, end));
    }
}
 
 
 
 
/*
run:
      
PT1.754859235S
      
*/

 

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Answer 4

import java.util.Calendar;
import java.util.Date;

public class MyClass {
     public static int getMonthFromCurrentDate() {
        Date date = new Date();
          
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
  
        return cal.get(Calendar.MONTH) + 1;
    }
    public static void test(long sum) {
        sum += 1;
    }
    public static void main(String args[]) {
        long startTime = System.nanoTime();
        
        // program
        long sum = 0;
        for (int i = 1; i <= 1_000_000; i++) {
			    sum += 1;
			    sum += 2;
			    test(sum);
			    int month = getMonthFromCurrentDate();
		}
		// program

        long endTime = System.nanoTime();
        long totalTime = endTime - startTime;
        
        System.out.println(totalTime + " nanoseconds");
    }
}
 
 
 
 
/*
run:
      
1761862795 nanoseconds
      
*/

 

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