内部类的四种实现方式

内部类分为四种：

1.成员内部类
2.局部内部类
3.静态内部类
4.匿名内部类

1.成员内部类

Java code

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//成员内部类......相当于非静态方法
class MemberInner {
    private int a = 3;

    public class Inner2 {
        private int a = 2;

        public void doSomething() {
            // 调用外部类的属性
            System.out.println(MemberInner.this.a);// 这块要注意......很重要！！！
            System.out.println(a);
        }
    }
}

public class Test3 {
    public static void main(String[] args) {
        MemberInner.Inner2 inner2 = new MemberInner().new Inner2();// 非静态内部类要new实例
        inner2.doSomething();
    }
}

2.静态内部类

Java code

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//静态内部类......相当于静态方法
class StaticInner{
    private static int a=3;
    public static class Inner{
        public void test(){
            System.out.println(a);
        }
    }
}

public class Test2 {
    public static void main(String[] args) {
        StaticInner.Inner inner=new StaticInner.Inner();//静态内部类直接调用
        inner.test();
    }
}

3.局部内部类

Java code

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//局部内部类......相当于局部变量
class LocalInner {
    public void doSomething(int b) {
        final int a = 3;// 只能访问final的变量
        class Inner3 {
            public void test(int b) {
                System.out.println(b);
                System.out.println(a);
            }
        }
        new Inner3().test(b);
    }
}

public class Test4 {
    public static void main(String[] args) {
        LocalInner inner = new LocalInner();
        inner.doSomething(4);
    }
}