Thread: Why doesn't the frame viewer print the rectangles?

I am trying to draw two rectangles in a new frame, and I am making some mistake which I can't figure out. It should be easy but I just don't see it.

Here are the two classes:


Drawn rectangles:

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;
 
//Draws two rectangles
 
 
public class Four
{
	public void paintComponent(Graphics g)
	{
		Graphics2D g2 = (Graphics2D) g;
 
		Rectangle box = new Rectangle(5,10,10,10);
		g2.draw(box);
 
		box.translate(15,25);
		g2.draw(box);
	}
}

And the frame:

import java.awt.Component;
import javax.swing.JFrame;
 
public class BoxViewer 
{
	public static void main(String[] args)
	{
		JFrame frame = new JFrame();
 
		frame.setSize(300,400);
		frame.setTitle("Two Rectangles");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
		Four component = new Four(); //Mixes up both classes
 
		frame.add(component); //Error is here
 
		frame.setVisible(true);
	}
 
}

You should check the error message in detail, and post it here as it will tell you what you're doing wrong. You need to add a Component or one of its children to a JFrame, and your Four class doesn't extend anything. Perhaps you want to have it extend an existing JComponent type of class.

Originally Posted by curmudgeon

You should check the error message in detail, and post it here as it will tell you what you're doing wrong. You need to add a Component or one of its children to a JFrame, and your Four class doesn't extend anything. Perhaps you want to have it extend an existing JComponent type of class.

That is correct! Thank you very much.

You're quite welcome! So, out of curiosity, what class did you have Four extend?