eclipse中的错误：未解决的编译

Question

i have this code

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;
        // ......
    }
}

It works fine from the command prompt but when i try to run the code in eclipse it gives me the following error:

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)

What should i do??

Answer 1

From Documentation :

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

syntax:

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

you need Outer class instance to create an instance of your Inner class.

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

Answer 2

I think you cannot call innerClass inside form Static method of its own.

import javax.swing.JFrame;
public class testFrame {
public static void main(String[] args) {
    // TODO Auto-generated method stub


}
private void getMe(){
    wmmain m = new wmmain();
    m.setSize(800,500);
    m.setVisible(true);
}
class wmmain extends JFrame /* MAIN WINDOW */
{
    public wmmain(){

    }
     }
     }

Try this . it will work . or you can use the answer of PermGenErroｒ

Answer 3

If the wmmain class is not using member variables from watermark and you want to hide the window class, then you could also declare wmmain as a private static inner class:

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

    private static class wmmain extends JFrame {
        JMenuBar jmb;
        // ......
    }
}