Fundamentals - SCJP Sun Certified Programmer for Java Platform SE6 - page 54

FIGURE 1.15 Computing the exclusive or expression 12^45

12
45
12^45

0000 1100
0010 1101
0010 0001

The result is 00100001 in binary, which is 33 in decimal. Therefore, the value of result
is 33.
The & , ^ , and | are also logical operators, meaning they can operate on boolean types.
The result of each operator is identical to Table 1.2 if you were to replace each 0 with false
and each 1 with true . For example, the AND operator

& is only true when both operands
are true . The inclusive OR operator | is only false when both operands are false . The
exclusive OR is only true when the two operands are different.
What is the output of the following logical statements?

3. int a = 5, b = 10, c = 0;
4. boolean one = a < b & c != 0;
5. System.out.println(one);
6. boolean two = true | true & false;
7. System.out.println(two);
8. boolean three = (c != 0) & (a / c > 1);
9. System.out.println(three);

The variable one on line 4 is the result of true & false , which is false . The result of
two on line 6 might surprise you. The & operator has a higher precedence than | , so the
true & false is evaluated fi rst, which results in false . Then true | false is evaluated,
which is true , so two evaluates to true .
You might think that the Boolean on line 8 evaluates to false , but that line of code
actually throws an ArithmeticException when attempting to compute a / c . The value
of c is 0 and integer division by 0 is undefi ned in Java. Therefore, the last println never
executes.
The example of a / c is a typical situation where a conditional operator comes in
handy. The conditional operators && and || short-circuit, meaning the right operand may
not get evaluated if the left hand operand can determine the result.
For example, when using && , if the left operand is false , there is no need to check the
right operand. False AND anything is false . In this case, the right-hand expression is not
evaluated. Similarly, when using || , if the left operand is true , there is no need to check the
right operand because true OR anything is true .
The following statements are a modifi cation of the previous example, except this
time the logical expression short-circuits. What is the value of three after the following
statements?

21. int a = 5, b = 10, c = 0;
22. boolean three = (c != 0) && (a / c > 1);