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This article introduces the knowledge of "A brief introduction to the default and static methods of Java". Many people will encounter such a dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

What is the use of adding the default method to Java

Official answer: the default method allows you to add new functionality to the interface of an existing library and ensures binary compatibility with code written using the old version of the interface. This boring introduction seems difficult to understand. Let me give you a simple example. Suppose there is a big project, an interface is implemented by a lot of classes, and everyone runs smoothly and safely. Suddenly one day, there is a small problem, or there is a better optimization solution, which needs to be added to these implementation classes. Before the emergence of the default method, only abstract methods can be operated, and you need to give a specific definition in the implementation class, so you can only close your eyes and add directly from morning to night.

However, the appearance of the default method allows the specific implementation of the method to be given in the interface, and the default method can be implemented automatically in the implementation class. I just need to put this optimization in the default method of the interface to optimize all the implementation classes. Of course, it is purely personal understanding. If there is anything inappropriate in my example, you are welcome to correct it.

Package com.my.pac21;/** * @ auther Summerday * / interface Closable {void close (); / / suppose it is the new default method default void makeSound () {System.out.println ("peng!");}} interface Openable {default void makeSound () {System.out.println ("peng!");}} class Window implements Closable {@ Override public void close () {System.out.println ("Window.close") }} public class Door implements Closable, Openable {@ Override public void close () {System.out.println ("Door.close");} / / two interfaces contain methods with the same name, which need to be overridden. Specify a @ Override public void makeSound () {System.out.println ("need to override default methods");} public static void main (String [] args) {Closable cw = new Window (); Closable cd = new Door (); cw.close () / / Window.close cd.close (); / / Door.close / / implement the default method cw.makeSound (); / / peng! Cd.makeSound (); / / need to override default methods}}

What is the use of the new static method in Java

The appearance of default methods and static methods in the interface makes the interface lose the feature of "all abstract methods". After exploring the new default methods, it's time to start with static methods. Started frantically searching for information.

Before Java 8 made it possible to declare static methods in interfaces, it was common practice to place these methods in companion utility classes. For example, the java.util.Collections class is a companion to the java.util.Collection interface, and declares static methods that would be more appropriate in the relevant Java Collections Framework interfaces. You no longer need to provide your own companion utility classes. Instead, you can place static methods in the appropriate interfaces, which is a good habit to cultivate.

This is the answer I found on stack overflow. What do you mean? before adding static methods, if we want some fixed operations to appear in the interface, we must define an implementation class that matches the interface. With the emergence of static methods in the interface, static methods can be called directly through the interface.

Package com.my.pac21;/** * @ auther Summerday * / public class Test {public static void main (String [] args) {int val1 = 5; int val2 = 6; / / by creating an object that implements the class, Countable b = new CountableCompanion (); System.out.println (b.getNum (val1,val2)); / / call Countable.getMul (val1,val2) directly through the interface;} interface Countable {/ / ordinary abstract method int getNum (int Amenint b) / / static method static int getMul (int aline int b) {return aforb;}} / / implementation class class CountableCompanion implements Countable {@ Override public int getNum (int aline int b) {return aint b;}}

This is an example that I think is quite naive, just for understanding.

In the case of ordinary abstract methods: I define an abstract method in the interface, and then I define the implementation class that implements the method. Finally, I call the method by creating an instance of the implementation class, and finally calculate the sum of the two values. As you can imagine, in practice, this is troublesome if a method of the same nature wants to be implemented in multiple implementation classes.

The case of static methods: it is very comfortable to define static methods directly in the interface and can be called directly by the interface without the need to define the corresponding implementation classes.

This is the end of "A brief introduction to the default and static methods of Java". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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