java inner class, anonymous inner class

Java internal classes are divided into 4 types:

1) Static internal classes: Classes modified by static are called static classes. Putting static classes inside a class is called static internal classes

Features: Can access the outside world: static methods /Static properties, cannot access instance resources

Case:

import inner.Foo.Koo;//Be sure to import the Koo static inner class

public class Demo9 {

public static void main(String[] args) {

Koo koo = new Koo();

koo.add();

}

}

class Foo{

int a = 12;//Instance variable

static int aa=16;

public static void show(){ System.out.println("static method");}

//static inner class

static class Koo{

public void add(){

// System.out .println(a); Static inner classes cannot access instance resources (variables)

System.out.println(aa);

show();//Static inner classes can access static properties and methods of the outside world

}

}

}

2) Member inner class: Inside a class, a class without static modification is directly defined. When creating a member inner class object, the outer class must be created first.

Features: member inner class, can access external properties and methods

Case:

import inner.Foo1.Koo1;

public class Demo10 {

public static void main(String[] args) {

/ /Koo1 koo1 = new Koo1(); To create a member inner class, you must first create an external class object

Foo1 foo1 = new Foo1();

//Remember (written examination)

Koo1 koo1 = foo1. new Koo1();

koo1.show();

}

}

class Foo1{

int a =12;

static int aa = 16;

class Koo1{

void show() {

System.out.println(a+" , "+aa);

}

}

}

3) Local internal classes: very rarely used, characterized by defining a class within a method (enterprise development Medium and rarely used)

Features: local inner class, when referencing external variables, the variable must be modified with final

Case:

public class Demo11 {

public static void main(String[] args) {

final int a = 12;

final int b = 13;

class Foo2{

int c = 16;

public int add(){

//In the local inner class, refer to external variables , then the variable must be modified with final

return a+b+c;

}

}

Foo2 foo2 = new Foo2();

System.out.println(foo2.add());

}

}

4) Anonymous inner class: an inheritance of the original class

Features: used in combination with interfaces/abstract classes

eg new class name/interface name {

overridden method

};

Case:

public class Demo1 {

public static void main(String[] args) {

Koo koo = new Koo(){

// You can override the method

public String toString() {

Return "A Koo object is generated";

}

// New methods cannot be created in anonymous inner classes

// public void show(){

// System.out.println( "liu");

// }

};

System.out.println(koo);

// koo.show();

}

}

class Koo{

}

For more java internal classes and anonymous internal classes related articles, please pay attention to the PHP Chinese website!