Logical operators in Java

Logical operators in Java are used to combine multiple boolean expressions or conditions, and they are essential for writing decision-making logic like if statements and loops.

Logical AND (&&)

Returns true only if both conditions on either side are true. It uses short-circuit evaluation, meaning the second condition isn't checked if the first is already false.

int age = 25;
boolean hasID = true;
if (age >= 18 && hasID) {
    System.out.println("Entry allowed");
}

Logical OR (||)

Returns true if at least one of the two conditions is true. It also short-circuits — if the first condition is true, the second is never evaluated.

boolean isWeekend = true;
boolean isHoliday = false;
if (isWeekend || isHoliday) {
    System.out.println("No work today");
}

Logical NOT (!)

Reverses the value of a boolean expression — true becomes false and vice versa.

boolean isLoggedIn = false;
if (!isLoggedIn) {
    System.out.println("Please log in");
}

Truth Table

• true && true → true
• true && false → false
• false || true → true
• false || false → false
• !true → false

Short-Circuit Evaluation

Java also provides non-short-circuit versions, & and |, which always evaluate both sides. These are rarely used for boolean logic but matter to know, since && and || skip unnecessary evaluations for better performance and to avoid errors like calling a method on a null object.