你一定要知道Java中4种类型的内部类

在Java中有4种不同类型的内部类可以使用。下面给出它们的名称和例子。

1.静态嵌套类(Static Nested Classes)

class Outer {
    static class Inner {
        void go() {
            System.out.println("Inner class reference is: " + this);
        }
    }
}

public class Test {
    public static void main(String[] args) {
        Outer.Inner n = new Outer.Inner();
        n.go();
    }
}

输出：Inner class reference is: Outer$Inner@19e7ce87

2.成员内部类(Member Inner Class)

成员类是特定于实例的。它可以访问所有方法，字段和外部类本身的引用。

public class Outer {
    private int x = 100;

    public void makeInner(){
        Inner in = new Inner();
        in.seeOuter();
    }

    class Inner{
        public void seeOuter(){
            System.out.println("Outer x is " + x);
            System.out.println("Inner class reference is " + this);
            System.out.println("Outer class reference is " + Outer.this);
        }
    }

    public static void main(String [] args){
        Outer o = new Outer();
        Inner i = o.new Inner();
        i.seeOuter();
    }
}

输出：

Outer x is 100
Inner class reference is Outer$Inner@4dfd9726
Outer class reference is Outer@43ce67ca

3.局部方法内部类(Method-Local Inner Classes)

public class Outer {
    private String x = "outer";

    public void doStuff() {
        class MyInner {
            public void seeOuter() {
                System.out.println("x is " + x);
            }
        }

        MyInner i = new MyInner();
        i.seeOuter();
    }

    public static void main(String[] args) {
        Outer o = new Outer();
        o.doStuff();
    }
}

输出：x is outer

public class Outer {
    private static String x = "static outer";

    public static void doStuff() {
        class MyInner {
            public void seeOuter() {
                System.out.println("x is " + x);
            }
        }

        MyInner i = new MyInner();
        i.seeOuter();
    }

    public static void main(String[] args) {
        Outer.doStuff();
    }
}

输出：x is static outer

4.匿名内部类(Anonymous Inner Classes)

当您需要给一个GUI应用程序窗口小部件加一个动作监听器时，匿名内部类就会经常被用到。

button.addActionListener(new ActionListener(){
     public void actionPerformed(ActionEvent e){
         comp.setText("Button has been clicked");
     }
});

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