import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class IncrementDecrement extends JPanel implements MouseMotionListener{

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        JFrame frame = new JFrame("Decrement/Increment");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(new IncrementDecrement());
        frame.pack();
        frame.setVisible(true);
    }

    JLabel label;

    public IncrementDecrement() {
        addMouseMotionListener(this);
        add(label = new JLabel("Left side = red, Right Side = green"));
    }

    public Dimension getPreferredSize() {
        return new Dimension(400, 400);
    }

    @Override
    public void mouseDragged(MouseEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseMoved(MouseEvent e) {
        // TODO Auto-generated method stub
        if(e.getX() < this.getSize().getWidth()/2)
            setBackground(Color.RED);
        else
            setBackground(Color.GREEN);
    }

}