内部类

内部类的分类：

• 成员内部类
• 方法内部类
• 局部内部类
• 匿名类
• 静态内部类

1 成员内部类

是在一个类中声明的类，包含内部类的是外围类

成员内部类的访问权限：

• public可以在外围类的外部使用内部类创建对象
• private只能在外围类的内部使用内部类创建对象

创建对象：

• 成员内部类的建立依赖于外围类，在创建内部类的时候必须先用于外部类

public class Outter_v1 {
    public static void main(String[] args) {
        Outter01 out = new Outter01();
        Outter01.Inner in = out.new Inner();
        System.out.println(out.a);
        System.out.println(out.b);
        System.out.println(in.c);
        System.out.println(in.d);
    }
}
class Outter01{
    public int a = 0;
    public int b = 1;
    public class Inner{
        public int c = 2;
        public int d = 3;
    }
}

public class Outter_v2 {
    public static void main(String[] args) {
        Outter out = new Outter();
        Base in = out.fun();
        in.output();

        System.out.println(out.a);
        System.out.println(out.b);
        //System.out.println(in.c);  接口类型只能访问接口中声明的成员
        //System.out.println(in.d);
    }
}
interface Base{
    void output();
}
class Outter{
    public int a = 0;
    public int b = 1;

    public class neuqer implements Base{
        public void output(){
            System.out.println("我是东秦学生");
        }
    }

    public neuqer fun(){
        return new neuqer();
    }
}

内部类可以直接访问外部类的成员

public class Outter_v3 {
    public static void main(String[] args) {
        Outter03 out = new Outter03();
        Outter03.Inner in = out.new Inner();
        System.out.println(out.a);
        System.out.println(out.b);
        in.fun();
    }
}
class Outter03{
    public int a = 0;
    public int b = 1;
    public class Inner{
        public int c = 2;
        public int d = 3;
        public void fun(){
            System.out.println(a);
            System.out.println(b);
            System.out.println(c);
            System.out.println(d);
        }
    }
}

2 内部类的内存结构

• 内部类对象和外部类对象分别是两个不同的对象
• 内部类对象依赖于外围类对象，外围类对象是内部类对象的创建者
• 内部类对象中保存着外围类对象的一个引用，可与用来帮助内部类对象访问外围类对象的成员

public class Outter_v4 {
    public static void main(String[] args) {
        ouuter04 outter = new ouuter04();
        ouuter04.inner inner = outter.new inner();

        System.out.println(outter.a);
        System.out.println(outter.b);
        
        inner.fun();

        System.out.println(outter.a);
        System.out.println(outter.b);
        System.out.println(inner.c);
        System.out.println(inner.d);
    }
}
class ouuter04{
    public int a = 0;
    public int b = 1;
    public class inner{
        public int c = 2;
        public int d = 3;
        //内部类可以直接修改和访问外部类成员
        public void fun(){
            a = 4;
            b = 5;
        }
    }
}

3 内部类常见用法

• 隐藏类的实现细节
• 方便实现多重继承
• 实现外围类对于同一个接口不同实现

public class Outter_v5 {
    public static void animalCrazy(Animal an){
        an.run();
        an.say();
    }
    //加深了对于接口使用的认识
    public static void main(String[] args) {
        CreateAnimal crea = new CreateAnimal();
        Animal dog = crea.createdog();
        Animal cat = crea.crearecar();
        Animal bird = crea.createbird();
        animalCrazy(dog);
        animalCrazy(cat);
        animalCrazy(bird);
    }
}
interface Animal{
    public abstract void say();
    void run();
}
class CreateAnimal{
    private class dog_inter implements Animal {
        public void say(){
            System.out.println("汪汪汪......");
        }
        public void run(){
            System.out.println("四条腿跑");
        }
    }
    private class cat_inter implements Animal {
        public void say(){
            System.out.println("喵喵喵......");
        }
        public void run(){
            System.out.println("被追着跑");
        }
    }
    private class bird_inter implements Animal {
        public void say(){
            System.out.println("咕咕咕......");
        }
        public void run(){
            System.out.println("翅膀飞");
        }
    }
    public dog_inter createdog(){return new dog_inter();}
    public cat_inter crearecar(){return new cat_inter();}
    public bird_inter createbird(){return new bird_inter();}
}

}
}
public dog_inter createdog(){return new dog_inter();}
public cat_inter crearecar(){return new cat_inter();}
public bird_inter createbird(){return new bird_inter();}
}