double d1 = 0.666 * 5; // fast but obscure and inaccurate: convert
System.out.println(d1); // 2/3 to 0.666 in programmer's head
double d2 = 2/3 * 5; // wrong answer - 2/3 == 0, 0*5.0 = 0.0
System.out.println(d2);
double d3 = 2d/3d * 5; // "normal"
System.out.println(d3);
double d4 = (2*5)/3d; // one step done as integers, almost same answer
System.out.println(d4);
int i5 = 2*5/3; // fast, approximate integer answer
System.out.println(i5);
