java - eclipse 错误:unresolved compilation

Question

我有这个代码

public class watermark {

    public static void main(String[] args) {
        wmmain m = new wmmain();
        m.setSize(800, 500);
        m.setVisible(true);
    }

    class wmmain extends JFrame /* MAIN WINDOW */
    {
        JMenuBar jmb;
        // ......
    }
}

它在命令提示符下运行良好，但是当我尝试在 eclipse 中运行代码时，出现以下错误:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
No enclosing instance of type watermark is accessible. Must qualify the allocation with an enclosing instance of type watermark (e.g. x.new A() where x is an instance of watermark).

at watermark.main(watermark.java:20)

我该怎么办？？

Answer 1

来自 Documentation :

To instantiate an inner class, you must first instantiate the outer class.

语法:

OuterClass.InnerClass innerObject = outerObject.new InnerClass();

您需要外部类实例来创建内部类的实例。

wmmain m=new WaterMark().new wmmain();