Double value calculation and type cast in Java

/*from w ww .  ja v  a2 s . c o m*/
public class Main {
  public static void main(String[] u) {

    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
    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);
  }
}