public class Primzahlenpaar {
private boolean isPrim(int number) {
if (number <= 1) return false;
for (int i = 2; i < number; i++) if (number % i == 0) return false;
return true;
}

private void next(int i) {
if (isPrim(i)) if (isPrim(i + 2)) System.out.println(i + " - " + (i + 2));
}

public static void main(String[] args) {
int endwert = 30;
Primzahlenpaar prim = new Primzahlenpaar();
for (int i = 1; i <= endwert - 2; i++) prim.next(i);
}
}