Thread: multi array of buttons

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.*;
 
public class Screen implements ActionListener 
{
	JButton[][] b=new JButton[200][200];
 
	Screen()
	{
		JFrame j = new JFrame("A Star Algorithm");
		j.setSize(700,500);
		j.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		j.setLayout(new GridLayout(20,20));
		j.setResizable(true);
 
		//create Buttons
		for(int row=0;row<200;row++)
		{
			for(int col=0;col<200;col++)
			{
				b[row][col]=new JButton();
				j.add(b[row][col]);
				b[row][col].addActionListener(this);
			}
 
		}
 
		j.setVisible(true);
	}
 
	public void actionPerformed(ActionEvent e)
	{
 
	}
}

I am trying to program an A* algorithm and I cannot even get past the buttons. I need a 2D array of buttons to handle this problem but I am getting the following errors.

at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)
	at java.awt.AWTEventMulticaster.componentShown(AWTEventMulticaster.java:162)

//create Buttons
		for(int row=0;row<200;row++)
		{
			for(int col=0;col<200;col++)
			{
				b[row][col]=new JButton();
				b[row][col].setBackground(Color.RED);
				b[row][col].addActionListener(this);
				j.add(b[row][col]);
			}
		}

Please help this is not creating a multi array of buttons

Why 200 x 200 buttons in a 20 x 20 grid?

What happens if you add a main() method and create an instance of Screen?

When you're asking for help with errors or code that doesn't do what you think it should, provide compilable, runnable code that demonstrates the problem. With a few minor changes (mostly scaling the buttons to 20 x 20) and a main() method, your code works fine for me.