Boolean Expressions

Boolean expressions evaluate to true or false.

Example:
int score = 85;

if(score >= 90){
System.out.println("A");
}

else if(score >= 80){
System.out.println("B");
}

else {
System.out.println("C");
}
The program checks conditions in order and prints the grade based on the score.

Comparison operators:
== (equals), != (not equals), >, <, >=, <=

Logical operators:
&& (AND), || (OR), ! (NOT)

Boolean Order of Operations:

Example:
int x = 5;
if(x > 3 && x < 10){
System.out.println("Valid");
}

Both conditions must be true for the message to print.

int x = 5;
boolean result = x > 3 && x < 10 || x == 20;

First: x > 3 → true

Then: x < 10 → true

Then: true && true → true

Then: x == 20 → false

Finally: true || false → true

Final result: true

The AND is evaluated before the OR, which is why the expression is grouped that way.

Short-Circuit Evaluation:

Short-circuiting means Java stops evaluating early if it already knows the result.

AND (&&) Short-Circuit

If the first condition is false, Java stops immediately.

Example:
int x = 5;

if(x > 10 && x < 20){
System.out.println("Hello");
}

Since AND requires both sides to be true, one false already makes the whole thing false.

OR (||) Short-Circuit

If the first condition is true, Java stops immediately.

Example:
int x = 5;

if(x < 10 || x > 100){
System.out.println("Hello");
}

Since OR only needs one true, Java doesn’t check the second condition.