Summary and sharing of anonymous inner classes in Java

This article mainly introduces the relevant information on the summary of anonymous internal classes in java. I hope this article can help everyone. Friends in need can refer to

Summary of anonymous internal classes in java

Anonymous inner classes are inner classes without names

Because they have no names, anonymous inner classes can only be used once. They are usually used to simplify code writing

But there is a prerequisite for using anonymous inner classes: you must inherit a parent class or implement an interface

Example 1: Do not use anonymous inner classes to implement abstract methods

abstract class Person { 
  public abstract void eat(); 
} 
  
class Child extends Person { 
  public void eat() { 
    System.out.println("eat something"); 
  } 
} 
  
public class Demo { 
  public static void main(String[] args) { 
    Person p = new Child(); 
    p.eat(); 
  } 
}

Running result: eat something

As you can see, we use Child to inherit the Person class, and then implement a Child instance, upcast it into a reference to the Person class

However, if the Child class here is only used once, wouldn't it be troublesome to write it as an independent class?

At this time, anonymous inner classes were introduced

Example 2: Basic implementation of anonymous inner classes

 public abstract void eat(); 
} 
  
public class Demo { 
  public static void main(String[] args) { 
    Person p = new Person() { 
      public void eat() { 
        System.out.println("eat something"); 
      } 
    }; 
    p.eat(); 
  } 
}

Run results: eat something

As you can see, we directly implemented the methods in the abstract class Person in braces

This way, we can omit the method of a class Writing

And, anonymous inner classes can also be used on interfaces

Example 3: Using anonymous inner classes on interfaces

interface Person { 
  public void eat(); 
} 
  
public class Demo { 
  public static void main(String[] args) { 
    Person p = new Person() { 
      public void eat() { 
        System.out.println("eat something"); 
      } 
    }; 
    p.eat(); 
  } 
}

Run result: eat something

As can be seen from the above example, as long as a class is abstract or an interface, then in its subclass All methods can be implemented using anonymous inner classes

The most common situation is in the implementation of multi-threading, because to implement multi-threading you must inherit the Thread class or inherit the Runnable interface

Example 4: Anonymous inner class implementation of Thread class

public class Demo { 
  public static void main(String[] args) { 
    Thread t = new Thread() { 
      public void run() { 
        for (int i = 1; i <= 5; i++) { 
          System.out.print(i + " "); 
        } 
      } 
    }; 
    t.start(); 
  } 
}

Running result: 1 2 3 4 5

Example 5: Anonymous inner class implementation of Runnable interface

public class Demo { 
  public static void main(String[] args) { 
    Runnable r = new Runnable() { 
      public void run() { 
        for (int i = 1; i <= 5; i++) { 
          System.out.print(i + " "); 
        } 
      } 
    }; 
    Thread t = new Thread(r); 
    t.start(); 
  } 
}

Running results: 1 2 3 4 5

The above is the detailed content of Summary and sharing of anonymous inner classes in Java. For more information, please follow other related articles on the PHP Chinese website!