Anonymous inner class is also an inner class without a name
Because there is no name, the anonymous inner class can only be used once, and it is often used to simplify code writing
However, there is a precondition for using anonymous inner classes: You must inherit from a parent class or implement an interface.
Example 1: Implementing an abstract method without using anonymous inner classes
Abstract classPerson { Public Abstract voideat ();} classChildextendsPerson { Public voideat () {System.out.println ("Eat Something"); }} Public classDemo { Public Static voidMain (string[] args) {person P=NewChild (); P.eat (); }}
running result:eat something
As you can see, we inherit the person class with child, and then we implement an instance of child and transform it upward into a reference to the person class.
However, if the child class here is used only once, wouldn't it be a hassle to write it as a separate class?
The anonymous inner class is introduced at this time.
Example 2: Basic implementation of anonymous inner classes
Abstract classPerson { Public Abstract voideat ();} Public classDemo { Public Static voidMain (string[] args) {person P=NewPerson () { Public voideat () {System.out.println ("Eat Something"); } }; P.eat (); }}
running result:eat something
As you can see, we directly implement the methods in the abstract class person in curly braces.
This allows you to omit the writing of a class
Also, anonymous inner classes can be used on interfaces
Example 3: Using an anonymous inner class on an interface
Interface Person { publicvoidpublicclass Demo { Public Static void Main (string[] args) { new person () { publicvoid eat () { System.out.println ("eat Something"); } ; P.eat (); }}
running result:eat something
As can be seen from the above example, 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
An anonymous inner class implementation of the instance 4:thread class
Public class Demo { publicstaticvoid main (string[] args) { new Thread () { publicvoid run () { for (int i = 1; I <= 5; i++) { + "");}} ; T.start (); }}
operating Result:1 2 3 4 5
An anonymous inner class implementation of the instance 5:runnable interface
public class Demo { public static void main (string[] args) {Runnab Le r = new Runnable () { public void run () { for (int i = 1; I <= 5; I++ + "" = new Thread (r); T.start (); }}
operating Result:1 2 3 4 5
Anonymous internal Class 2 (reprint)