Ridimensionamento JPanel in base alla dimensione del Frame

[Patrick Jane]

Ridefinire paintComponent() è corretto.
Ma non sarebbe più semplice fare così?

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

class MiddlePanel extends JPanel {
  
  MiddlePanel() {
    super(new BorderLayout());
  }
  
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    
    Graphics2D g2 = (Graphics2D) g;
    
    int width = getWidth();
    int height = getHeight();

    for(int i=0; i<width; i+=20) {
      g.drawLine(i,0,i,height);
      g.drawLine(0,i,width,i);
    }
  }
}

class FrameExample extends JFrame {
  private MiddlePanel mp;
  
  FrameExample() {
    mp = new MiddlePanel();
    add(mp);
    
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }
  
  public static void makeGUI() {
    FrameExample fe = new FrameExample();
    fe.setSize(800,600);
    fe.setVisible(true);
  }
  
  public static void main(String[] args) {
    try {
      SwingUtilities.invokeAndWait(new Runnable() {
        public void run() {
          makeGUI();
        }
      });
    } catch(Exception e) {}
  }
}