Java 8 Method references

Java 8 New Features

Method references point to a method by the method's name.

Method references make the language structure more compact and concise, reducing redundant code.

Method references are denoted by a pair of colons :: .

Below, we define the 4 This method is used as an example to differentiate in Java 4 different method references.

package com.w3codebox.main;
　
@FunctionalInterface
public interface Supplier<T> {
　　　　T get();
}
　
class Car {
　　　　//Supplier is a jdk1.8interface, here used with lambda together
　　　　public static Car create(final Supplier<Car> supplier) {
　　　　　　　　return supplier.get();
　　　　}
　
　　　　public static void collide(final Car car) {
　　　　　　　　System.out.println("Collided "　+　car.toString());
　　　　}
　
　　　　public void follow(final Car another) {
　　　　　　　　System.out.println("Following the "　+　another.toString());
　　　　}
　
　　　　public void repair() {
　　　　　　　　System.out.println("Repaired "　+　this.toString());
　　　　}
}

• Constructor reference:Its syntax is Class::new, or more generally Class<T>::new, for example:

  final Car car = Car.create(Car::new);
  final List<Car> cars = Arrays.asList(car);

• Static method reference:Its syntax is Class::static_method, for example:

  cars.forEach(Car::collide);

• Method reference to any object of a specific class:Its syntax is Class::method, for example:

  cars.forEach(Car::repair);

• Method reference to a specific object:Its syntax is instance::method, for example:

  final Car police = Car.create(Car::new);
  cars.forEach(police::follow);

Method reference example

In Java8Tester.java file input the following code:

import java.util.List;
import java.util.ArrayList;
　
public class Java8Tester {
　　　public static void main(String args[]){
　　　　　　List<String> names = new ArrayList<>();
　　　　　　　　
　　　　　　names.add("Google");
　　　　　　names.add("w3codebox");
　　　　　　names.add("Taobao");
　　　　　　names.add("Baidu");
　　　　　　names.add("Sina");
　　　　　　　　
　　　　　　names.forEach(System.out::println);
　　　}
}

In this example, we use the System.out::println method as a static method reference.

Execute the above script, and the output will be:

$ javac Java8Tester.java　
$ java Java8Tester
Google
w3codebox
Taobao
Baidu
Sina

Java 8 New Features