Generate random number based on time

I try to generate random number with this code :

public class RandomInt {
private Random generator = new Random(System.currentTimeMillis());
double randomGenerator(){
    return generator.nextDouble()*0.5;

}
public static void main(String[] args) {
    new RandomInt();
}
        }   

But when run the file, it shows nothing. Help me with this please. Thank you

PS : I'm newbie