Slick2D rendering every 0.8

Question

I am trying to make the game change the wave of the moles every 0.8 seconds. (My game is simply "Whack The Moles, for practicing).

My code to change waves:

double TIME = 0.8;

if (Next) { //If 0.8 seconds is up
        if (Over == false) { //make sure the game hasn't ended
            start = (int) (cTime/1000); //cTime is the milisecond since game started
            String wave = MolesWaves.RandomWave(); //getting the new wave data 
            initWave(wave); 
            Next = false; //disallow the game from changing wave
        }
    }
    else {
        if (((cTime/1000) - start) >= TIME) { //changing speed
            System.out.println("Test: " + ((cTime/1000)-start));
            Next = true; //allow game to change waves
        }
    }

From the System.out.println("Test: " + ((cTime/1000)-start)); , this is what i get from the output log.

Test: 0.802
Test: 0.817
Test: 0.833
Test: 0.852
Test: 0.867
Test: 0.883
Test: 0.9
Test: 0.917
Test: 0.933
Test: 0.95
Test: 0.967
Test: 0.983
Test: 1.0

The problem is that the waves changes 13 times every second, it stop switching once it reached every second for a while then starts it again.
If the value of TIME is 1, everything is fine. The waves changes every 1 seconds.
I am using 0.8 as i am trying to implement a Difficulty selection(Easy, medium, hard...) The harder it is, the faster the wave changes.

Is the code above the culprit to my problem? If it is, please solve this for me.

Answer 1

We don't see the type of start, but I'm assuming it's a double. If so the culprit is this line:

start = (int) (cTime/1000); //cTime is the milisecond since game started

Imagine cTime is 900 and the last wave started at time 0 (so a new wave should be starting). Then when this new wave starts, you'll set start = (int)(900/1000); This is a truncating integer division, so the new value of start is 0. But this is the same as the old value -- so since nothing has changed, a new wave will start again immediately the next time the time condition is checked.

Instead of doing an integer division, convert the integer cTime to a double and perform the division and the comparison in floating point:

start = ((double) cTime) / 1000.0;
// ...
if ((((double)cTime/1000.0) - start) >= TIME) { //changing speed

The new value of start in the scenario above should then be 0.9, and the new round should be allowed to last for 0.8 seconds.