In-depth analysis of Java’s interface callback mechanism

java interface callback details

Interface callback is a way to reflect polymorphism. It allows the object reference of a class that implements an interface to be assigned to the interface variable declared by the interface, so that the methods in the interface implemented by the class can be called through the interface variable. Doing so is equivalent to notifying the corresponding object to call the interface method, also known as interface callback. When different classes use the same interface, they may have different functional implementations, which means that the method bodies in the interface can be different. Therefore, different behaviors can be achieved through interface callbacks.

public interface IntefaceHuidiao {

void showMessage();

}

public class PC implements IntefaceHuidiao {

public void showMessage() {

System. out .println ("I am a computer!");

}

}

public class TV implements IntefaceHuidiao {

public void showMessage() {

System.out.println（＂I am a TV!＂）;

}

}

public class TestIntefaceHudiao {

public static void main(String[] args) {

IntefaceHuidiao ms ;

ms = new TV();

ms.showMessage();

ms = new PC();

ms.showMessage();

}

}

Why should java use interface callbacks

How to explain it specifically may not be particularly easy to explain....

Let me show you a program I just wrote...it's easy to understand...

interface Msg{

void showMessage();

}

class NbMsg implements Msg{

public void showMessage() {

System.out.println(＂123456＂);

}

}

class CahrMsg implements Msg{

public void showMessage() {

System.out.println(＂abcdef＂);

}

}

public class test {

private Msg msg;

public void show() {

System.out.println("Processing something");

msg.showMessage();

}

public void setMsg(Msg msg) {

this.msg = msg;

}

public static void main(String[] args) {

test a = new test();

a.setMsg(new CahrMsg());

a.show();

a.setMsg(new NbMsg());

a.show();

}

}

turn out:

Deal with something

abcdef

Deal with something

123456

Why interfaces can implement callbacks

Interface callback means that the reference of an object created using a class that implements an interface can be assigned to the interface variable declared by the interface, and then the interface variable can call the method of the interface implemented by the class. In fact, when an interface variable calls a method in the interface implemented by the class, it notifies the corresponding object to call the interface method. This process is called the interface callback of the object function. See the example below.

interface people {

void peoplelist();

}

class student implements people {

public void peoplelist() {

system.out.println("i'm a student.");

}

}

class teacher implements people {

public void peoplelist() {

system.out.println("i'm a teacher.");

}

}

public class example {

public static void main(string args[]) {

people a; // Declare interface variables

a = new student(); // Instantiation, the reference to the object is stored in the interface variable

a.peoplelist(); //Interface callback

a = new teacher(); // Instantiation, the reference to the object is stored in the interface variable

a.peoplelist(); //Interface callback

}

}

result:

i'm a student.

i'm a teacher.

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