Understand the idea

A boolean has one of two values: true or false. Build conditions with comparisons, combine them with && and ||, and read the whole expression as a question. Short-circuit operators can skip evaluating the right-hand side when the left side determines the result.

Explore the details

Java Booleans

A boolean is the simplest data type in Java — it can only ever be true or false. Booleans are the foundation of every decision your program makes.

• Is the user logged in? → boolean isLoggedIn = true;
• Is the light on? → boolean isLightOn = false;
• Is it raining? → boolean isRaining = true;

Code anatomy / கோடின் விளக்கம்

Boolean Expressions

In practice, booleans are rarely written as literals. They are almost always the result of an expression — a comparison that Java evaluates to true or false:

Real-Life Example: Voting Age

Booleans shine when you use them to make decisions. Here we check if a person is old enough to vote (age ≥ 18) and print a different message depending on the result:

Combining Booleans

You can combine boolean expressions using logical operators to build more complex conditions:

int age = 20;
boolean isAdult   = (age >= 18);  // true
boolean hasTicket = true;

// Logical operators
boolean canEnter = isAdult && hasTicket;  // true (both true)
boolean eitherOr = isAdult || hasTicket;  // true (at least one)
boolean notKid   = !isAdult;             // false (inverts true)

System.out.println(isAdult);    // true
System.out.println(canEnter);   // true
System.out.println(notKid);     // false

A complete runnable example

This complete Main.java program focuses on the lesson idea. Reference fragments above may demonstrate individual statements; this example includes the imports, entry point, and supporting types it needs.

public class Main {
    public static void main(String[] args) throws Exception {
        int age = 20;
        boolean hasTicket = true;
        boolean canEnter = age >= 18 && hasTicket;
        System.out.println(canEnter);
        System.out.println(!hasTicket);
    }
}

true
false

Change it. Run it. Understand it.

Load this lesson example into the editor. Change one value or statement, predict the result, then press RUN to execute Java.

Make it your own

Your learning checkpoint

• Explain the example without reading the output first.
• Make the change requested in the practice task.
• Describe why the result changed—or why compilation failed.

Ready to move on? Follow the next lesson in course order, or return to the curriculum to review a prerequisite.