Movement

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

public class Movement extends JFrame 
    implements ActionListener {

    private JButton upButton, downButton, rightButton, leftButton;
    private JPanel panel;
    
    private int xPos;
    private int yPos;

    public static void main(String[] args) {
        Movement frame = new Movement();
        frame.setSize(700, 500);
        frame.createGUI();
        frame.setVisible(true);
    }

    private void createGUI() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        Container window = getContentPane();
        window.setLayout(new FlowLayout() );

        panel = new JPanel();
        panel.setPreferredSize(new Dimension(600, 400));
        panel.setBackground(Color.white);
        window.add(panel);
        
        upButton = new JButton("Up");
        window.add(upButton);
        upButton.addActionListener(this);
        
        downButton = new JButton("Down");
        window.add(downButton);
        downButton.addActionListener(this);
        
        rightButton = new JButton("Right");
        window.add(rightButton);
        rightButton.addActionListener(this);
        
        leftButton = new JButton("Left");
        window.add(leftButton);
        leftButton.addActionListener(this);
        
        xPos = 300;
        yPos = 200;
        
        panel.setFocusable(true);
        panel.requestFocus();
        
        panel.addKeyListener(new KeyListener() {
            @Override
            public void keyPressed(KeyEvent e) {
                switch (e.getKeyCode()) {
                    case 87:
                    case KeyEvent.VK_UP:
                    moveCircle(0, yPos - 15);
                    break;
                    case 68:
                    case KeyEvent.VK_RIGHT:
                    moveCircle(xPos + 15, 0);
                    break;
                    case 83:
                    case KeyEvent.VK_DOWN:
                    moveCircle(0, yPos + 15);
                    break;
                    case 65:
                    case KeyEvent.VK_LEFT:
                    moveCircle(xPos - 15, 0);
                    break;
                }
 
                System.out.println(e.getKeyCode());
            }
 
            @Override
            public void keyReleased(KeyEvent e) {
 
            }
 
            @Override
            public void keyTyped(KeyEvent e) {
 
            }
        });
    }

    public void moveCircle(int x, int y) {
        Graphics paper = panel.getGraphics();
        paper.fillOval(xPos, yPos, 15, 15);
        
        paper.setColor(Color.white);
        paper.fillOval(xPos, yPos, 15, 15);
        yPos = yPos + y;
        xPos = xPos + x;
        xPos = (xPos + 585) % 585;
        yPos = (yPos + 385) % 385;
        paper.setColor(Color.black);
        paper.fillOval(xPos, yPos, 15, 15);

    }
    public void actionPerformed(ActionEvent event) {
        Object source = event.getSource();
        if (source == upButton) {
            moveCircle(0, -15);
        }
        
        if (source == downButton) {
            moveCircle(0, 15);
        }
        
        if (source == rightButton) {
            moveCircle(15, 0);
        }
        
        if (source == leftButton) {
            moveCircle(-15, 0);
        }
    }
}