Java BooleanSupplier Interface with examples

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Welcome to Java 8 Series. In this tutorial, you will learn about the Java BooleanSupplier Interface with examples.

BooleanSupplier is a Functional interface introduced as part of Java 8. It is available in java.util.function package.

What is the use of BooleanSupplier interface?

This interface is mainly used for just getting a boolean-valued result which is not based on the input. BooleanSupplier interface doesn’t have any input arguments. Consider a case where we need to write a lambda expression which has no input argument and return a boolean-valued result. BooleanSupplier just supplies the result of the boolean-valued type.

Example

public class StaticReference
{
    public static void main(String[] args)
    {
        Operation ops = () -> {
            return true;
        };
        boolean result = ops.getValue();
        System.out.println(result);
    }

    interface Operation
    {
        boolean getValue();
    }
}

When you look at the above example, we have a function interface with an abstract method which doesn’t have any input argument but returns a boolean value. So a lambda expression needs a target type which needs to be a functional interface and in this example, it is Operation interface.

Instead of creating our own function interface for this scenario, Java has provided us a BoooleanSupplier interface. Let now see in-depth details on Java BooleanSupplier Interface with examples.

BoooleanSupplier Interface

@FunctionalInterface
public interface BoooleanSupplier 

BoooleanSupplier interface contains an operation that doesn’t have input argument and returns a boolean value

It is a functional interface and the functional method is getAsBoolean().

Method description

boolean getAsBoolean()

Example of BoooleanSupplier interface using lambda

public class StaticReference
{
    public static void main(String[] args)
    {
        BooleanSupplier supplier = () -> {
            return true;
        };
        boolean result = supplier.getAsBoolean();
        System.out.println(result);
    }
}

Example of BooleanSupplier interface using a Method reference

public class StaticReference
{
    public static void main(String[] args)
    {
        BooleanSupplier supplier = StaticReference::get;
        boolean result = supplier.getAsBoolean();
        System.out.println(result);
    }

    static boolean get()
    {
        return true;
    }
}

If you want to write a lambda expression with no arguments and returns a boolean-valued result, please use Java BooleanSupplier interface.

References

Java 8 BooleanSupplier official documentation

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