Increment

[Vishnu Prakash]

 class Red {
  public int a;
  public static int b;
  public static void main (String[] in) {
    Red r1 = new Red(), r2 = new Red();
    r1.a++;
    r1.b++;
    System.out.print(r1.a+", "+r1.b+", "+r2.a+", "+r2.b + "," +b);
  }
}
 

Output: 1 1 0 1 1

I couldn�t understand how r2.b and b are evaluating to 1 and why r2.a is evaluating to 0.

[Mike Gershman]

There are 2 instances (objects) of Red. r1 refers to the first. r2 refers to the other.

There are two copies of a, one in each object. r1.a refers to the first copy, r2.a refers to the other copy.

Thete is one copy of the static member variable b. It can be refered to as b, Red.b, r1.b, or r2.b, but there is still only one copy.

All three are member variables so they are initialized to 0. r1.a and the one and only b are then incremented to 1. r2.a is left at 0.

In the print line, the same b is printed three times.
[ January 02, 2005: Message edited by: Mike Gershman ]