Can someone please tell me if my guess below is correct? boolean b1, b2, b3, b4; b1 = b2 = b3 = b4 = true; int x = (b1 | b2 & b3 ^ b4)? x++: --x; System.out.println("Result: " + x);

Result: 0 Since (b1 | b2 & b3 ^ b4) evaulates to true, we postfix increment x, then we prefix decrement x --> which gets us back to x = 0. BUT if (b1 | b2 & b3 ^ b4) were to evaluate to false, we would SKIP the x++ and jump to to what's beyond the colon: (--x)? If so, then x = -1. So: - We only execute what's between ? and : (in this case, x++) if the statement inside the parentheses is TRUE? - But we execute the code AFTER the : (in this case, --x) no matter what? In other words: x = (test)? x++: --x if test is true do everything after the question mark? if test is false do everything after the colon? Thanks! I know this was a long post. Susan

[This message has been edited by Susan Delph (edited May 01, 2001).]

Hi Susan, The statement is broken up into the following: boolean expression ? true choice : false choice I am not sure what x starts out as because you don't show the initialization. But we can take an example: String s = (b1 | b2 & b3 ^ b4) ? "True" : "False"; will yield s = "True". Regards, Manfred.

Susan Delph
Ranch Hand

Joined: Feb 24, 2001
Posts: 34

posted

0

Hi Manfred, This was a test question from my Java class. Here's the entire question: What is the value displayed by the following program?

Answers: A. -1 B. 0 C. 1 D. 2 According to the instructor, the correct answer is 0. I verified this by comiling and executing the code. It IS 0. But - I'm not sure why. When I changed the line to: b1 = b2 = b3 = b4 = false; the result was -1. Susan

Manfred Leonhardt
Ranch Hand

Joined: Jan 09, 2001
Posts: 1492

posted

0

Hi Susan, Now I see the problem, sorry. By your results we can see that we are actually dealing with: x = x++; This is the old post increment operator. Since we are starting with 0 this is the compilation steps: 1. Save current value or x (store 0) 2. Increment variable referenced by x (x = 1) 3. Assign saved value to variable referenced by x (x = 0) Therefore, we get no change in x because the increment happened and then the assignment nullified it! Regards, Manfred.

Susan Delph
Ranch Hand

Joined: Feb 24, 2001
Posts: 34

posted

0

Hi Manfred, Thank you, for both explanations! I understand now.... Susan