Understanding of the Java callback interface

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Now there are two classes, one is a, one is B, the callback is a to call a method in B, and then B callback a method in a, this method is the callback method, the callback mechanism is inseparable from the interface. That is, Class A implements an interface and implements the interface method, and Class B gets a reference to the callback function, and then calls the swap function. It seems to be more around, give a popular example.

Now there is a teacher (Class A) and a student (class B), the teacher told the student said, put your homework to the office, the students said my homework has not finished, and so on, and then handed over, the teacher said well, so told the students where his office, and then the teachers and students to go to busy their own things. (This example also has async, will not be involved in the code to be asynchronous), after the meeting, the students handed over to the teacher designated office.

Here's a look at the code:

Callback interface equivalent to the teacher's office address

Public interface CallBack {

public void callback (String homework);

}

Teacher appears as an upper-level application

public class Teacher implements callback{

@Override

public void callback (String homework) {

System.out.println ("Teacher, this is my homework ..." +homework);

}

}

Students appear as lower-level identities

public class Student {

Equivalent to the teacher's office

Private CallBack CallBack = null;

public void Setcallback (CallBack CallBack) {

This.callback = CallBack;

}

public void Dohomework () {

System.out.println ("The Writing industry ... (half an hour later) the homework was finished ");

Tell the teacher that the homework has been finished and has been handed over to the office

Callback.callback ("A math paper");

}

}

public class Test {

public static void Main (string[] args) {

Teacher t = new Teacher ();

Student s = new Student ();

Incoming callback object teacher

S.setcallback (t);

S.dohomework ();

}

}

The above is an example of a callback. Callback is a callback interface, is the office address, the teacher is in the upper level, its students do not know and do not understand, so the teacher wants to let the students will work to the office, also must tell the student office address, so the teacher this class must go to implement this callback interface. In this class of teachers, you can also call a method of the student class, of course, in this case, not to call the Student class method, but only to implement the callback function, tell the students his homework received. In the student class, we first get a reference to the callback interface, which is the address of the office, and then the student class calls the callback function and puts the job into the office.

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Understanding of the Java callback interface