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1. Inner class
Define a class inside other classes, this class is called an inner class.
- According to the internal class, the definition position is different, and it is divided into member internal class and local internal class
- Member inner class : the inner class is located in the member position of the outer class
- Local inner class : the inner class is located in the member method of the outer class
For example:
class A{
//成员内部类：位于外部类的成员位置
class B{
}
public void show(){
//局部内部类，位于外部类成员方法内
class C{
}
}
}
1. Member inner class
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Access characteristics of member inner classes
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The inner class can directly access the members of the outer class, including private ones.
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To access the members of the inner class, the outer class must create an inner class object
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You can create internal class objects directly outside, format
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External class name. Internal class name Object name = new external class (). New internal class ()
-
note
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The class cannot be privatized, but the internal class can (often used is the privatization of the internal class, the form of external indirect access to ensure data security)
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Internal classes can be modified with static, called static internal classes, which can only access static members of external classes (for easy access to data)
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The format of the static inner class directly created by the outside world
-
Wai.Nei a = new Wai.Nei ();
For example:
public class 内部类的访问特点 {
public static void main(String[] args) {
//可以在外部直接创内部类的对象
Outer.Inner inner1=new Outer().new Inner();
inner1.neishow();
Outer outer=new Outer();
outer.waishow();
}
}
class Outer{
int num=100;
private int a=200;
class Inner{
int b=300;
public void neishow(){
System.out.println(b);
//内部类可以发访问外部类的成员，包括私有成员
System.out.println(num);
System.out.println(a);
waishow1();
}
public void neitest(){
System.out.println("内部类方法执行");
}
}
public void waishow(){
System.out.println("外部的show方法执行");
//外部类访问内部类的成员，必须创建内部类的对象
Inner inner=new Inner();
//通过内部类对象，访问内部类的成员变量
System.out.println(inner.b);
//通过内部类对象，访问内部类的成员方法
inner.neitest();
}
private void waishow1(){
System.out.println("外部类私有方法执行");
}
}
2. Local inner class
- Access characteristics of local internal classes
- Can directly access members of external classes
- You can create internal class objects and call internal class methods through objects to use internal class functions
- Local internal class access to local variables must be final modification
For example:
public class 局部内部类 {
public static void main(String[] args) {
int a=100;
int b=200;
Outer outer=new Outer();
outer.waishow(100,200);
}
}
class Outer{
private int num=20;
public void waishow(final int a,final int b){
//该局部变量需要使用final修饰
final int num1=30;
//局部内部类定义在成员方法内
class inner{
public void neishow(){
num=40;
System.out.println(num);
System.out.println(num1);
System.out.println(a+":"+b);
}
}
//创建内部类对象，调用内部类功能
inner x = new inner();
x.neishow();
}
}
3. Anonymous inner class
It is a simplified way of writing local inner classes.
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Prerequisite: There is a class (can be an abstract class) or interface; format:
new class name or interface name () { rewrite method; };
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Nature:Anonymous objects that inherit this class or subclasses that implement this interface
For example:
//抽象类
abstract class AbstractClass{
public abstract void show();
}
class Outer1{
public void method(){
//创建抽象类的子类的匿名对象
new AbstractClass(){
@Override
public void show() {
System.out.println("shoshowshow");
}
};
}
}
//接口
public interface MyInter{
public abstract void show();
}
class Outer{
public void method(){
new MyInter(){
@Override
public void show() {
System.out.println("showshowshow");
}
};
}
}