Boolean Expression

A Boolean expression returns a boolean value: true or false.

This is useful to build logic and find answers.

For example, you can use a comparison operator, such as the greater than (>) operator, to find out if an expression (or a variable) is true or false:

int x = 10;
int y = 9;
System.out.println(x > y); // returns true, because 10 is higher than 9

Or even easier:

System.out.println(10 > 9); // returns true, because 10 is higher than 9

In the examples below, we use the equal to (==) operator to evaluate an expression:

int x = 10;
System.out.println(x == 10); // returns true, because the value of x is equal to 10

System.out.println(10 == 15); // returns false, because 10 is not equal to 15

Real Life Example

Let's think of a "real life example" where we need to find out if a person is old enough to vote.

In the example below, we use the >= comparison operator to find out if the age (25) is greater than or equal to the voting age limit (18):

int myAge = 25;
int votingAge = 18;
System.out.println(myAge >= votingAge);

Cool, right? An even better approach would be to wrap the code above in an if...else statement, so we can perform different actions depending on the result:

int myAge = 25;
int votingAge = 18;
 
if (myAge >= votingAge) {
  System.out.println("Old enough to vote!");
} else {
  System.out.println("Not old enough to vote.");
}