Logical Operators

The three logical operators in the AP subset are AND, OR, and NOT. These operators are represented by the following symbols in Java:

AND        &&
OR         || (two vertical bars)
NOT        !

These logical operators allow us to combine conditions. For example, if a dog is gray and weighs less than 15 pounds it is the perfect lap dog.

The && (and) operator requires both operands (values) to be true for the result to be true.

(true && true) -> true
(true && false) -> false
(false && true) -> false
(false && false) -> false

The following are Java examples of using the && (and) operator.

((2 < 3) && (3.5 > 3.0)) -> true
((1 == 0) && (2 != 3)) -> false

The && operator performs short-circuit evaluation in Java. If the first operand in && statement is false, the operator immediately returns false without evaluating the second half.

The || (or) operator requires only one operand (value) to be true for the result to be true.

(true || true) -> true
(true || false) -> true
(false || true) -> true
(false || false) -> false

The following is a Java example of using the || (or) operator.

((2+3 < 10) || (19 > 21)) -> true

The || operator also performs short-circuit evaluation in Java. If the first half of an || statement is true, the operator immediately returns true without evaluating the second half.

The ! operator is a unary operator that changes a boolean value to its opposite.

(! false == true) -> true
(! true == false) -> true
(! true == true) -> false
!(2 < 3) -> false