通常通过继承某个类或实现某个接口的方式来编写代码，但是有时候某一些代码只使用一次，就没有必要写专门写一个子类或实现类了，可以采用匿名内部类的写法。最常用的场景是线程方面的应用。

一、不使用匿名内部类

①继承
abstract class Player
{
 public abstract void play();
}

public class FootBallPlayer extends Player

{
 public void play()
 {
  System.out.println("踢足球");
 }
}

public class AnonymousInnerClassTest

{
 public static void main(String[] args)
 {
  Player p1 = new FootBallPlayer();
  p1.play();
 }
}

②接口

interface IPlayer
{
 public void play();
}

public class IPlayFootballImpl implements IPlayer

{
 public void play()
 {
  System.out.println("踢足球");
 }
}

public class AnonymousInnerClassTest

{
 public static void main(String[] args)
 {
  
  IPlayer ip1 = new IPlayFootballImpl();
  ip1.play();
 }
}

二、使用匿名内部类
①继承
abstract class Player
{
 public abstract void play();
}

public class AnonymousInnerClassTest

{
 public static void main(String[] args)
 {
  Player p2 = new Player() {
   public void play()
   {
    System.out.println("打篮球");
   }
  };
  p2.play();
 }
}

②接口

interface IPlayer
{
 public void play();
}

public class AnonymousInnerClassTest

{
 public static void main(String[] args)
 {
  
  IPlayer ip2 = new IPlayer() {
   public void play()
   {
    System.out.println("打篮球");
   }
  };
 }
}

三、线程中的应用

实现线程的方法有两种：①继承Thread类 ②实现Runnable接口。给出用匿名类实现的例子：

public class ThreadTest

{
 public static void main(String[] args)
 {
  // 继承Thread类
  Thread thread = new Thread() {
   @Override
   public void run()
   {
    while (true)
    {
     try
     {
      Thread.sleep(1000);
      System.out.println(Thread.currentThread().getName());
      System.out.println(this.getName());
     }
     catch (InterruptedException e)
     {
      System.out.println(e.getMessage());
     }
    }
   }
  };
  thread.start();

  // 实现Runnable接口

  Thread thread2 = new Thread(new Runnable() {
   @Override
   public void run()
   {
    while (true)
    {
     try
     {
      Thread.sleep(1000);
      System.out.println(Thread.currentThread().getName());
     }
     catch (InterruptedException e)
     {
      System.out.println(e.getMessage());
     }
    }
   }
  });
  thread2.start();
 }
}