Java ++ operator

Question

So I was testing out operators, because im helping my friend with java and i stumbled across a weird order of programming. What is happening when I run the following code

public static void main(String[] args) {
    int B = 6;
    //First console print out
    System.out.println(B+=++B);
    System.out.println(B);
    B = 6;
    //Second Console print out
    System.out.println(B+=B++);
    System.out.println(B);
}

The output for the following code is

13
13

12   
12

What causes the second console B math output = 12 when it adds 6 to itself, followed by ++ (which is +1)

Answer 1

The difference here is in the increment operators.

In the case of B += ++B, B is incremented to 7 and added to its old self (6) to achieve 13.

In the case of B += B++, B is added to itself, giving 12, then the ++ is performed and the result stored in B, but the result of the calculation is then stored over the ++ in B. Thus giving 12 as the output.

Answer 2

ACTION       EFFECT   NOTES
----------   ------   -----
B = 6        B = 6
B += (++B)   B += 7   // B is incremented and the value is returned
B            B = 13

B = 6        B = 6
B += (B++)   B += 6   // The current value of B is the result of (B++) and B is
                      // incremented *after* the (B++) expression; however, the
                      // assignment to B (+=) happens after the (++) but it does
                      // not re-read B and thereby covers up the post increment.
B            B = 12