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.

public class Main {
  public static void main(String[] args) {
    boolean isJavaFun = true;
    boolean isFishTasty = false;
    System.out.println(isJavaFun);     // Outputs true
    System.out.println(isFishTasty);   // Outputs false
  }
}

Boolean Expressions

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.

public class Main {
  public static void main(String[] args) {
    int x = 10;
    int y = 9;
    System.out.println(x > y); // returns true, because 10 is higher than 9
  }
}

Booleans are the cornerstone of all conditional logic in Java, which you will learn about in the next chapter.