boolean

Learn true/false values with boolean.

What is boolean?

boolean is a type that can take only two values: true and false. It is used for logical decisions and flags.

boolean active = true;
boolean ready = false;

A boolean variable usually holds the result of a condition. For example userInput > 0 produces true or false.

Boolean values are written without quotes. "true" is a String, while true is a boolean.

Exercise Define a boolean and print it

Write a Main class with a main method. Assign true to boolean active. Print it with println.

Show example solution

public class Main {
    public static void main(String[] args) {
        boolean active = true;
        System.out.println(active);
    }
}

What is boolean used for?

Boolean variables are usually flags that steer the program flow. They hold whether a feature is on/off, whether a user is signed in, or whether a file exists.

An if condition expects a boolean inside its parentheses:

boolean signedIn = true;
if (signedIn) {
    System.out.println("Welcome");
}

That is why comparisons (>, ==) produce a boolean.

Test yourself

Match the boolean concepts

true

True
false

False
boolean

Logical type
!

Not
&&

And
Which is a valid boolean value?
- 42
- true
- "yes"
- 1
Show answer

true — boolean can only be true or false.
Assign a value to a boolean variable
```
boolean active = ____;
```
Show answer
```
boolean active = true;
```

Next lesson: String

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