Boolean Data Type in Java

The Boolean data type is the simplest primitive type in Java. It is used to represent truth values: true or false.

boolean

boolean flag;
  • Size (conceptual): 1 bit (but in JVM, it is usually stored as 1 byte = 8 bits, because JVM does not allocate memory smaller than a byte).
  • Possible Values:
    • true
    • false
  • Default Value: false
  • Usage: Used in conditions, loops, decision-making (if, while, for, etc.), and logical operations.

Internal Representation

  1. Java does not allow numeric to boolean conversion directly (unlike C/C++, where 0 = false and non-zero = true).
  2. In JVM, true is internally stored as 1, and false as 0, but you cannot directly use integers in place of boolean.

    Invalid:

    boolean b = 1; // Compilation error

    Correct:

    boolean b = true;

Example in Java

public class BooleanExample {
    public static void main(String[] args) {
        boolean isStudentLoggedIn = true;   // student has logged into ShikshaSanchar
        boolean hasPremiumAccess = false;   // free account, no premium access

        System.out.println("Is student logged in? " + isStudentLoggedIn);
        System.out.println("Does student have premium access? " + hasPremiumAccess);

        // Using in conditions
        if (isStudentLoggedIn) {
            System.out.println("Welcome to ShikshaSanchar!");
        }

        if (hasPremiumAccess) {
            System.out.println("Access granted to premium study materials.");
        } else {
            System.out.println("Upgrade to premium for exclusive content.");
        }
    }
}

Output:

Is student logged in? true

Does student have premium access? false

Welcome to ShikshaSanchar!

Upgrade to premium for exclusive content.

Explanation:

  • boolean in Java stores only two values: true or false (default = false).
  • It is used to represent conditions, decisions, and logical states.
  • In this example:
    • isStudentLoggedIn = true → prints true, so the message “Welcome to ShikshaSanchar!” is displayed.
    • hasPremiumAccess = false → prints false, so instead of premium content, the user sees “Upgrade to premium for exclusive content.”
  • Unlike C/C++, Java does not allow numbers to act as booleans (e.g., 1 is not true).
  • Thus, booleans are essential for decision-making and control flow in Java programs.

Important Points

  1. Only true or false are valid for boolean — no integers or strings.
  2. boolean cannot be typecasted to/from numeric types. 
    int a = 1;
// boolean b = (boolean)a; ❌ Not allowed
  3. Useful in control flow statements if, while, for, do-while.
  4. Often used with logical operators
    • && (AND)
    • || (OR)
    • ! (NOT)

Summary:

  • boolean = 1 bit (conceptually), stored as 1 byte in JVM.
  • Values: true or false only.
  • Default: false.
  • Usage: Widely used in decision-making and logical conditions.

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