Java problem

davholla · 09-25-2005, 02:53 PM

I am learning Java and I am having a problem with this code

Code:

import java.awt.*;
import javax.swing.*;

public class MyDrawPanel extends JPanel {
public void paintComponent(Graphics g) {
                g.setColor(Color.orange);
                g.fillRect(20,50,100,100);
        }}

It compiles but does not run it gives the error :-

Code:

Exception in thread "main" java.lang.NoSuchMethodError: main

How do I put a main method here ?

mrcheeks · 09-25-2005, 03:18 PM

You need to understand java basics before programming in java to avoid waste of your time.
To be "runnable" a class needs a main method which is static .

You need to add a "panel" in a window("a frame") to display it.

Here is a working code, not tested, but should work without problems.

Code:

import java.awt.*;
import javax.swing.*;

public class MyDrawPanel extends JPanel {
public void paintComponent(Graphics g) {
                g.setColor(Color.orange);
                g.fillRect(20,50,100,100);
        }

// if a main method the code inside the main method will be executed
public static void main(String args[]){

// create a window with a title
JFrame frame = new JFrame("MyApplication");

// if the window is closed, the program should exit
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

// add our beautiful panel inside the window
frame.getContentPane.add(new MyDrawPanel());

// prepare the gui and display it
frame.pack();
frame.setLocation(200,200);
frame.setSize(400,400);
frame.setVisible(true);
}
}

davholla · 09-26-2005, 02:38 AM

thank you