Java---Anonymous class summary

Learning Android today, one way to implement the OnClick event for a button control is to use an anonymous class, where anonymous classes in Java are summarized.

Anonymous inner class--an inner class without a name, because it has no name, so it can only be used once

Anonymous inner class--it is often used to simplify code writing

Use anonymous inner class prerequisites: You must inherit from a parent class or implement an interface

Note: As long as a class is abstract or an interface, the methods in its subclasses can be implemented using anonymous inner classes;

The most common situation is in the implementation of multithreading , because to implement multithreading must inherit the thread class or inherit the Runnable interface

1: Examples of implementations that do not use anonymous classes

1 Abstract classperson{2     Abstract voideat ();3 }4 5 classStudentextendsperson{6     voideat () {7System.out.println ("Student eat!");8     }9 }Ten  Public classInnerclass { One      Public Static voidMain (string[] args) { APerson Stu =NewStudent (); - stu.eat (); -     } the  -}

Output Result: >student eat!

Implementation process: The student class inherits the person class, implements an instance as its subclass, and translates it upward into a reference to the person class.

2: Anonymous inner class basic implementation mode

1 Abstract classperson{2      Public Abstract voideat ();3 }4 5  Public classInnerclass {6      Public Static voidMain (string[] args) {7Person Stu =NewPerson () {8              Public voideat () {9System.out.println ("Student eat!");Ten             } One         }; A stu.eat (); -     } -  the}

Output Result: >student eat!

Implementation: Put the abstract method eat () in the person class directly into the curly braces, note that there is a semicolon after the curly braces!

3: Anonymous inner class used on interface

1 Interfaceperson{2      Public Abstract voideat ();3 }4 5  Public classInnerclass {6      Public Static voidMain (string[] args) {7Person Stu =NewPerson () {8              Public voideat () {9System.out.println ("Student eat!");Ten             } One         }; A stu.eat (); -     } -  the}

Output Result: >student eat!

4: Implementation of anonymous classes in thread threading class

(1) Implementation of the Run () method in the Thread class

1  Public classInnerclass {2      Public Static voidMain (string[] args) {3Thread T =NewThread () {4              Public voidrun () {5                  for(inti = 0; I < 5; i++){6System.out.println ("x =" + i + ";"));7                 }8             }9         };Ten T.start (); One     } A  -}

Output Result:

x = 0;
x = 1;
x = 2;
x = 3;
x = 4;

(2) Implementation using the Runnable interface

1  Public classInnerclass {2      Public Static voidMain (string[] args) {3Runnable r =NewRunnable () {4              Public voidrun () {5                  for(inti = 0; I < 5; i++){6System.out.println ("x =" + i + ";"));7                 }8             }9         };Ten         Thread t = new  thread (r);  One T.run (); A     } -  -}

The result is the same as above, and the thread and the runnable are connected by the instance R of Runnable.

5: Extension: In Android Development button Implementation Onclicklistener () event using anonymous inner class implementation The main code is as follows:

1 /*2 * Initialize button control;3 * Set button listener to implement click action through Listener4          */5Loginbutton =(Button) Findviewbyid (r.id.button1);6Loginbutton.setonclicklistener (NewOnclicklistener () {7              Public voidOnClick (View args0) {8SYSTEM.OUT.PRINTLN ("Welcome!" ");9             }Ten});

Note that the implementation of the entire Onclicklistener () event is contained in the Setonclicklistener () method

Java---Anonymous class summary