JavaBooleans

Java Booleans

Very often in programming, you will need a data type that can only have one of two values, like:

• YES / NO
• ON / OFF
• TRUE / FALSE

For this, Java has aboolean data type, which can storetrue orfalse values.

Boolean Values

A boolean type is declared with theboolean keyword and can only take the valuestrue orfalse:

boolean isJavaFun = true;boolean isFishTasty = false;System.out.println(isJavaFun);    // Outputs trueSystem.out.println(isFishTasty);  // Outputs false

In practice, booleans are most often the result of expressions, and are used to test conditions in programs (see below).

Boolean Expressions

A boolean expression returns a boolean value:true orfalse.

This is useful to build logic and make decisions in programs.

For example, you can use acomparison operator, such as thegreater 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 greater than 9

Or even easier:

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

In the examples below, we use theequal 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) isgreater than ORequal to the voting age limit, which is set to18:

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

An even better approach would be to wrap the code above in anif...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.");}