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
• TRUE / FALSE

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

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

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.

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

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

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