Flow Control - SCJP Sun Certified Programmer for Java Platform SE6 - page 191

17. public static void main(String [] args) {
18. showGrade(77);
19. showGrade(54);
20. }
21.}
After an if expression evaluates to true and its corresponding block of code executes,
control leaves the if-then-else statement. For example, when grade equals 77 , line 7 is
true and line 8 executes, printing C . Line 9 is also true , but it is not evaluated because
control jumps out of the if statement to line 14.
When grade equals 54 , none of the if statements are true , so the else on line 11
executes and an F displays. The output of the Grades program is
C is your grade
F is your grade
Note that at most one block of code in an if-then-else control structure executes. The
last else block is always optional. When no else block appears, no block of code executes
if all the boolean expressions are false . Otherwise, when an if-then-else does contain
an ending else block, exactly one block of code in the control structure executes: either the
fi rst if condition to evaluate to true , or the else block if all if conditions are false .
Be Careful with boolean Comparisons
Watch out for assignment statements that look like boolean expressions. For example,
look at the following code and see if you can determine its output:
12. boolean b = false;
13. if(b = true) {
14. System.out.println(“true”);
15. } else {
16. System.out.println(“false”);
17. }
This code compiles fi ne. On line 13, b = true is an assignment, not a comparison. The
result of this boolean assignment is the value of b after the assignment, which is true .
Therefore, the output of this code is
true
Keep an eye out for this type of question on the exam.