Question

I use if(pause == null) to do something when pause is null. But I get the error

the operator == is undefined for the argument type(s) long,null

Here is the code,

public class Timer extends CountDownTimer {
    long pause = (Long) null;

    public Timer(long startTime, long interval) {
        super(startTime, interval);
    }

    @Override
    public void onTick(long millisUntilFinished) {
        content.setText("Tijd over: " + millisUntilFinished / 100);
    }

    public void onPause(long millisUntilFinished) {
        if(pause == null) {
            pause = millisUntilFinished;
            content.setText("Tijd over: " + millisUntilFinished / 100);
            this.cancel();
        }
        else {
            this.start();   
        }
    }

    @Override
    public void onFinish() {
        content.setText("Tijd is op!");
    }
}

This class isn’t finished, so ignore the rest of the code.

Answer 1

The variable pause is a long, so pause can never be null, and the compiler is confused. Either make it a Long, or use some in-band indicator of invalidity.