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Java Booleans

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

For this, Java has a boolean data type, which can store true or false values.

Boolean Values

A boolean type is declared with the boolean keyword and can only take the values true or false:


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

Try it Yourself »

However, it is more common to return boolean values from boolean expressions, for conditional testing (see below).

Boolean Expression

A Boolean expression is a Java expression that returns a Boolean value: true or false.

This is useful when we want to compare values to 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:


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

Try it Yourself »

Or even easier:


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

Try it Yourself »

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

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

Try it Yourself »

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, which is set to 18:


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

Try it Yourself »

The Boolean value of an expression is the basis for all Java comparisons and conditions.

You will learn more about conditions in the next chapter.

Test Yourself With Exercises


Fill in the missing parts to print the values true and false:

 isJavaFun = true;
 isFishTasty = false;

Start the Exercise