LongPredicate Interface in Java 8 with examples

LongPredicate Interface is a part of the java.util.function package which is introduced in Java 8. It is an in-built Functional Interface. This function expect one long-valued argument as an input and produces a boolean value as an output. As it is a functional interface, it can be used assignment target for lambda expression or method reference. In this post, we are going to see several implementations of LongPredicate Interface by using different examples.

LongPredicate Interface in Java 8 with Examples...!!! Share on X

Look at LongPredicate Javadoc description below:

LongPredicate Interface contains 4 methods:

1. test

2. and

3. or

4. negate

Let’s discuss these methods:

test 

This method evaluates predicate on the given long-valued argument and produces a boolean result.

boolean test(long value);

and 

This method returns a composed predicate that represents a short-circuiting logical AND of this predicate and another. When evaluating the composed predicate, if this predicate is false, then the other predicate is not evaluated.

default LongPredicate and(LongPredicate other) {
        Objects.requireNonNull(other);
        return (value) -> test(value) && other.test(value);
    }

or 

This method returns a composed predicate that represents a short-circuiting logical OR of this predicate and another. When evaluating the composed predicate, if this predicate is true, then the other predicate is not evaluated.

default LongPredicate or(LongPredicate other) {
        Objects.requireNonNull(other);
        return (value) -> test(value) || other.test(value);
    }

negate 

This method returns a predicate that represents the logical negation of this predicate.

default LongPredicate negate() {
        return (value) -> !test(value);
    }

Lets understand above mentioned methods through various examples:

Example 1. ‘test’ method

import java.util.function.LongPredicate;

public class LongPredicateInterfaceJava8Example1 {

    public static void main(String[] args) {

        System.out.println("LongPredicate Interface - Example 1");

        //Lambda implementation 
        LongPredicate longPredicateObj1 = i -> (long) i == -10;

        //Anonymous Class implementation
        LongPredicate longPredicateObj2 = new LongPredicate() {

            @Override
            public boolean test(long value) {
                return value > 100;
            }
        };
        System.out.println("Result Obj 1: " + longPredicateObj1.test(10));

        System.out.println("Result Obj 2: " + longPredicateObj2.test(5000));
    }

}

Example 2. ‘and’, ‘or’ and ‘negate’ methods

import java.util.function.LongPredicate;

public class LongPredicateInterfaceJava8Example2 {

    public static void main(String[] args) {

        System.out.println("LongPredicate Interface - Example 2");

        LongPredicate longPredicateObj1 = i - > i >= 10;

        LongPredicate longPredicateObj2 = i - > i == 5;

        LongPredicate longPredicateObj3 = i - > i < 70;

        //and operation
        System.out.println("Result 1: " + longPredicateObj1.and(longPredicateObj2).test(15));

        //or operation
        System.out.println("Result 2: " + longPredicateObj1.or(longPredicateObj2).or(longPredicateObj3).test(15));

        //negate operation
        System.out.println("Result 3: " + longPredicateObj3.negate().test(10));
    }

}

Java 8 LongPredicate Interface is an absolute useful addition as part of ‘Functional Interfaces’ and can serve variety of purposes. It is quite powerful as it can be used as a higher order functions through lambda functions and above examples could help you to get better idea on how to implement it.

LongPredicate Interface in Java 8 with Examples...!!! Share on X

Do you like this Post? – then check my other helpful posts:

• Passing Function as a Parameter in another Method in Java 8
• Collection sorting using Lambda in Java 8
• Supplier Interface in Java 8 with Examples

Other Useful References:

• Java 8 Functional Interfaces
• Java 8 Predicate Interface