Thread: can someone tell me what's wrong with my code

import java.awt.Color;
import javax.swing.JFrame;
import java.awt.Graphics;
import javax.swing.JOptionPane;
 
public class Program2 extends JFrame {
 
    private static final int FRAME_SIZE = 500;
    private int numberOfLines;
 
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        Graphics canvas = getContentPane().getGraphics();
        int width = this.getContentPane().getWidth();
        int height = this.getContentPane().getHeight();
 
 
 
    public static void main(String[] args) {
        Program2 guiWindow = new Program2();
        guiWindow.setSize(FRAME_SIZE, FRAME_SIZE);
        guiWindow.setDefaultCloseOperation(EXIT_ON_CLOSE);
        String valueString;
        valueString = JOptionPane.showInputDialog("Enter the number of lines in the grid (10-40):");
        guiWindow.numberOfLines = Integer.parseInt(valueString);
        guiWindow.setVisible(true);
 
    }
}

It's highlighting the "public static void main" line in red, but when I post the paint method in that section, it highlights all of that in red too.

That was my problem, thank you. But now I have another question, I need to have an input trap error so that the user can only enter numbers from 10 to 40. How would I do that, would I use an "if" statement or what?

if (i > 10) && (i <40)

Make a function to get the user input. The use an if to see if the value is in the range. Then if the value is not in the wanted range say "Value must be: blah blah" and then run the function again

Or you could just as easily use a while:

while( i<10 && i>40)
{
//Get input method
}

To finish the program I have to draw the lines using the following rules:

-Whatever number the user entered, that’s how many horizontal and vertical lines should be in the grid.
-The lines should be evenly spaced.
-The border of the content pane, that is, the part that is between the border of the frame and the grid drawing, must be 10% of the content frame height and width.
-The grid must stretch and shrink based on the size of the content pane.

The height of the grid should always be 80% (0.8) of the height of the content pane.
The top and bottom borders should be 10% (0.1) of the content pane’s height.
The width of the grid should always be 80% (0.8) of the width of the content pane.
The left and right borders should be 10% (0.1) of the content pane’s width.

Resizing the window should cause the grid to distort to stay in place.
This can be done by using the height and width of the content pane to calculate where to draw your lines.


I'm totally lost on what the code should be for calculating all of this.