从另一个类调用内部类成员

Question

如果这个问题很愚蠢,请原谅我,因为我对JAVA程序完全陌生.我正在研究嵌套类的概念,并遇到以下程序.

// Demonstrate an inner class.
class Outer {
    int outer_x = 100;
    void test() {
        Inner inner = new Inner();
        inner.display();
    }
    // this is an inner class
    class Inner {
        void display() {
            System.out.println("Display: outer_x = " + outer_x);
        }
    }
}
class NestedClass {
    public static void main(String args[]) {
        Outer outer = new Outer();
        outer.test();

//      Inner inner = new Outer().Inner();
//      inner.display();
    }
}

而我的疑问是如何访问Inner类的成员NestedClass.在"Java - 完整参考"中,给出了它"You can, however, create an instance of Inner outside of Outer by qualifying its name with Outer, as in Outer.Inner".但如果我尝试使用它,

        Inner inner = new Outer().Inner();
        inner.display();

这是投掷错误.所以请帮助我的专家.

Answer 1

您需要Inner使用new关键字创建新实例.

Inner inner = new Outer().new Inner(); // "new" keyword is required to create a new Inner instance.

如果您没有import com.java.test.Outer.Inner;添加导入,请添加它.否则,你可以做这样的事情

Outer.Inner inner = new Outer().new Inner();