import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.Vector;
  
class TotalRedraw extends JPanel {
    final int NUM_ROWS = 500;
    final int CHECKERBOARD_SIZE = 20;

    JFrame window = new JFrame();
    // list of checkerboard rectangles
    Vector<CheckerboardRect> checkerboardObjs = new Vector<CheckerboardRect>();
    CheckerboardRect blackRect = new CheckerboardRect(10, 10, 100, 50, Color.black);
    
    // variables to handle state information while moving the black rectangle
    boolean moving = false;  // whether or not the rectangle is being moved
    int leftOffset; // the initial offset of the mouse from the upper
    int topOffset;  // left corner
    
    // checkerboard objects will store their color--inefficient storage-wise but
    // convenient and simplifies the paintComponent code
    class CheckerboardRect extends Rectangle {
	Color color;
	CheckerboardRect(int left, int top, int wd, int ht, Color c) {
	    super(left, top, wd, ht);
	    color = c;
	}
    }

    public TotalRedraw() {
	int row, col;
	boolean redFlag;
	CheckerboardRect r;
	// create a red and white checkerboard
	for (row = 0; row < NUM_ROWS; row++) {
	    // start with red on even rows and white on odd rows
	    redFlag = (row % 2 == 0);
	    for (col = 0; col < NUM_ROWS; col++) {
		r = new CheckerboardRect(col*CHECKERBOARD_SIZE,
					 row*CHECKERBOARD_SIZE,
					 CHECKERBOARD_SIZE, CHECKERBOARD_SIZE,
					 (redFlag ? Color.red : Color.white));
		// change the color of the next square
		redFlag = !redFlag;

		checkerboardObjs.add(r);
	    }
	}
	// code for drawing the black rectangle around the display
	addMouseListener(new MouseAdapter() {
		public void mousePressed(MouseEvent e) {
		    int x = e.getX();
		    int y = e.getY();
		    if (blackRect.contains(x,y)) {
			moving = true;
			leftOffset = x - (int)blackRect.getX();
			topOffset = y - (int)blackRect.getY();
		    }
		    repaint();
		}
		public void mouseReleased(MouseEvent e) {
		    if (moving) {
			moving = false;
			blackRect.setLocation(e.getX() - leftOffset,
					      e.getY() - topOffset);
		    }
		    repaint();
		}
	    });
	addMouseMotionListener(new MouseMotionAdapter() {
		public void mouseDragged(MouseEvent e) {
		    if (moving) {
			blackRect.setLocation(e.getX() - leftOffset,
					      e.getY() - topOffset);
			repaint();
		    }
		}
	    });
	window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	window.setContentPane(this);
	window.pack();
	window.setVisible(true);
    }
    public Dimension getPreferredSize() { return new Dimension(400, 400); }
    public Dimension getMinimumSize() { return new Dimension(400, 400); }

    public void paintComponent(Graphics g) {
	Graphics2D g2 = (Graphics2D)g;
	Color saveColor = g.getColor();
	// make the background white
	g2.setColor(Color.white); 
	g2.clearRect(0, 0, getWidth(), getHeight());

	// draw the checkerboard
        int i = 0; 
	for (CheckerboardRect r : checkerboardObjs) {
	    i++;
	    g2.setColor(r.color);
	    g2.fill(r);
	}

	// draw the black rectangle
	g2.setColor(blackRect.color);
	g2.fill(blackRect);

	g2.setColor(saveColor);
    }
    public static void main(String args[]) {
	javax.swing.SwingUtilities.invokeLater(new Runnable() {
		public void run() {
		    new TotalRedraw();
		}
	    });
    }
}