java继承内部类

测试了下一个类继承内部类

public class TestInner {
	public void testMethod() {		
		Outer outer = new Outer();
		Extend extendObj = new Extend(outer);
	}
	public static void main(String[] args) {
		(new TestInner()).testMethod();
	}
}
class Outer {
	public Outer() {
		System.out.println("Outer");
	}	
	class Inner {
		public Inner() {
			super();
			System.out.println("Inner");
		}
	}
}
class Extend extends Outer.Inner {
	public Extend(Outer outer) {		
		outer.super();
		System.out.println("Extend outer");
	}
}

比较纠结的地方是

Extend类的必须有以Outer实例为参数的构造函数，否则报错：

an enclosing instance that contains Outer.Inner is required