Loop including FPS

Question

How can I improve this main game loop that monitors and displays frames per second?

 public void run() {
 running=true;
 initengine();
 initgame();
 //Initialise game loop
 long looptime, difference=0,timetaken=0;
 int frames=0;
 fps=0;
 //Main game Loop
 while(running){
 while (timetaken < 1000 ){ 
 looptime=System.currentTimeMillis();
 update();
 render();
 try {
 Thread.sleep(1);
 } catch (InterruptedException ex) {
 System.out.println("Error");
 }
 frames++;
 timetaken+=difference;
 difference=(System.currentTimeMillis()-looptime); 
 }
 fps=frames;
 frames=0;
 timetaken=0;
 } 
System.exit(0);
}

Answer 1

A Thread.sleep(...) in the middle of your game loop is a problem. No-one wants to see that.

A really simple solution to this problem is do things a little differently....

long nextSecond = System.currentTimeMillis() + 1000;
int frames = 0;
while (running) {
 ....
 // Do your game loop work...
 ....
 frames++;
 long now = System.currentTimeMillis();
 if (now > nextSecond) {
 fps = frames;
 frames = 0;
 nextSecond = now + 1000;
 }
}

This removes the sleep, and the nested loop.