Java 8 : Predicates

What is Predicate?

Java 8 comes with a concept of functional interface. An interface having only one abstract method and any number of default and static methods is called a functional interface.

A Predicate (boolean-valued function) of one argument which is present in java.util.function package. It is predefined functional interfaces that It has only one abstract method i.e, test().

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interface Predicate<T> { public boolean test(T t); }

Predicate Example to check age is greater than 18 or not.

Step: -1

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public boolean test(Integer age) { if (age > 18) { return true; } else { return false; } }

Step -2

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public class PredicateExample { public static void main(String[] args) { Predicate<Integer> p = age -> (age > 18); System.out.println(p.test(21)); // true System.out.println(p.test(17)); // false } }

Predicate Example to check collection is empty or not

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package com.blogspot.ekumeedkiasha; import java.util.ArrayList; import java.util.Collection; import java.util.function.Predicate; public class PredicateExample { public static void main(String[] args) { Predicate<Collection> p = c -> c.isEmpty(); ArrayList<Object> al = new ArrayList<>(); al.add("Monday"); ArrayList<Object> al1 = new ArrayList<>(); System.out.println(p.test(al)); // false System.out.println(p.test(al1)); // true } }