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.
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:
1 2 3 4 5 6 7 8 9 | 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 = false 12 is greater than 8 = true
Predicate method with String argument
Consider the following code snippet:
1 2 3 4 5 6 7 8 9 10 11 12 | 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.
