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");
     }
});

你可能也会喜欢：

1.What Is Inner Interface in Java?
2.Why do we need Generic Types in Java?
3.An example problem of Generic types
4.Constructors of Sub and Super Classes in Java?

原文：4 types of Java inner classes