Predicate interface in Java 8 with examples

In this blog post, I will be explaining how the Java 8 functional interface Predicate works. To know more about functional interfaces, you can refer this blog post.

Edit

The Predicate interface provides a method called test. This method accepts a parameter of any data type and returns a boolean.

Predicate method with Integer argument

Consider the following code snippet:

public class PredicateDemo {public static void main(String[] args) {Predicate<Integer> greaterThan8 = (input) -> input > 8;System.out.println("4 is greater than 8 = "+greaterThan8.test(4));System.out.println("12 is greater than 8 = "+greaterThan8.test(12));}}

Here, the Predicate.test method checks if the input number is greater than 8. So when the above code is executed, it will print the following output:

4 is greater than 8 = false12 is greater than 8 = true

Predicate method with String argument

Consider the following code snippet:

import java.util.function.Predicate;public class PredicateDemo {public static void main(String[] args) {Predicate<String> startsWithHello = (str) -> str.startsWith("Hello");System.out.println("Hello World starts with Hello = "+startsWithHello.test("Hello World"));System.out.println("Test String starts with Hello = "+startsWithHello.test("Test String"));}}

Here, the Predicate.test method checks if the input String starts with the String “Hello”. So when the above code is executed, it will print the following output:

Hello World starts with Hello = true Test String starts with Hello = false

You can get the source code for this example along with the code for other Java 8 examples at the Github repository here.









































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