Java 8 | BooleanSupplier Interface with Examples

The BooleanSupplier interface is a specialized functional interface introduced in Java 8 and available in the java.util.function package. It represents a supplier of boolean-valued results that does not accept any input arguments and returns either true or false.

• Primitive specialization of Supplier<Boolean>.
• Avoids boxing and unboxing of Boolean objects.
• Supports lambda expressions and method references.

import java.util.function.BooleanSupplier;

public class Main {
    public static void main(String[] args) {

        BooleanSupplier isJavaFun =
            () -> true;

        System.out.println(isJavaFun.getAsBoolean());
    }
}

true

Explanation: In this example, the BooleanSupplier does not take any input. When the getAsBoolean() method is called, it returns true.

Syntax

@FunctionalInterface
public interface BooleanSupplier

Method of BooleanSupplier Interface

1. getAsBoolean() Method

The getAsBoolean() method is the functional method of the BooleanSupplier interface. It supplies a boolean result without accepting any input parameters.

• Takes no arguments.
• Returns a primitive boolean value.
• Avoids boxing and unboxing overhead.

Syntax:

boolean getAsBoolean()

Return Value: Returns either true or false.

import java.util.function.BooleanSupplier;

public class Main {
    public static void main(String[] args) {

        BooleanSupplier isEvenDay =
            () -> (10 % 2 == 0);

        System.out.println(isEvenDay.getAsBoolean());
    }
}

true

Explanation: The supplier evaluates the condition 10 % 2 == 0. Since 10 is divisible by 2, the condition is true and getAsBoolean() returns true.

Example: Java program to illustrate getAsBoolean() method of BooleanSupplier Interface

Java

import java.util.function.BooleanSupplier;

public class GFG {
    public static void main(String args[])
    {

        // Create a BooleanSupplier instance
        BooleanSupplier sup = () -> true;

        // Get the boolean value
        // Using getAsBoolean() method
        System.out.println(sup.getAsBoolean());
    }
}

true

Explanation: In this example, a BooleanSupplier is created using a lambda expression that always returns true. When the getAsBoolean() method is called, it executes the supplier and returns the boolean value true, which is then printed to the console.

Real-World Use Cases

• Feature flag checks.
• Validation conditions.
• Permission and access checks.
• Lazy evaluation of boolean expressions.
• Configuration and status checks.

Advantages of BooleanSupplier

• Avoids boxing and unboxing of Boolean objects.
• Improves performance when working with boolean values.
• Simplifies conditional logic using lambda expressions.
• Useful for lazy evaluation of boolean conditions.
• Supports functional programming in Java.
• Reduces boilerplate code.