Turtle Mouse Movement

package com.badui;

import java.awt.AWTException;
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Robot;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.InputEvent;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;

public class MouseTurtle extends JFrame implements ActionListener {

    private static final long serialVersionUID = -1318655831513696878L;

    private final JTextArea commands = new JTextArea();
    private final JTextField textField = new JTextField();

    private final Robot robot;

    private int mouseX, mouseY;
    private double angle = 0;

    public MouseTurtle(Robot robot) {
        super("Give me the sweet release of death");
        this.robot = robot;

        getContentPane().add(this.commands, BorderLayout.CENTER);
        getContentPane().add(this.textField, BorderLayout.SOUTH);

        this.commands.setPreferredSize(new Dimension(500, 200));
        this.commands.setEnabled(false);
        this.textField.setPreferredSize(new Dimension(500, 25));
        this.textField.addActionListener(this);

        robot.mouseMove(mouseX, mouseY);

        pack();
        setLocationRelativeTo((Component)null);
        setVisible(true);
        setResizable(false);
        this.textField.requestFocus();
    }

    private void parseCommand(String command) {
        String[] parts = command.split(" ");
        if(parts.length != 2 && !parts[0].equalsIgnoreCase("quit")) {
            printLine("Bad command!");
        } else {
            switch(parts[0].toLowerCase()) {
            case "forward":
                moveForward(parts[1], 1);
                break;
            case "backward":
                moveForward(parts[1], -1);
                break;
            case "turn":
                turn(parts[1]);
                break;
            case "mouse":
                if(parts[1].equalsIgnoreCase("down")) {
                    robot.mousePress(InputEvent.BUTTON1_DOWN_MASK);
                } else if(parts[1].equalsIgnoreCase("up")) {
                    robot.mouseRelease(InputEvent.BUTTON1_DOWN_MASK);
                } else {
                    printLine("Bad mouse click");
                }
                break;
            case "quit":
                System.exit(0);
                break;
            default:
                printLine("Bad command");
                break;
            }
        }
    }

    private void moveForward(String distStr, double mul) {
        try {
            double dist = Double.parseDouble(distStr) * mul;
            double dx = dist * Math.cos(angle);
            double dy = dist * Math.sin(angle);
            mouseX += (int)dx;
            mouseY += (int)dy;
            robot.mouseMove(mouseX, mouseY);
            printLine("Took " + dist + " steps forward");
        } catch(NumberFormatException e) {
            printLine("Enter a number!");
        }
    }

    private void turn(String angleStr) {
        try {
            double angle = Math.toRadians(Double.parseDouble(angleStr));
            this.angle = (this.angle + angle) % (2 * Math.PI);
            printLine("Turned around by " + Math.toDegrees(angle) + " degrees");
        } catch(NumberFormatException e) {
            printLine("Enter a number!");
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        parseCommand(this.textField.getText());
        this.textField.setText("");
    }

    private void printLine(String line) {
        if(this.commands.getText().isEmpty()) {
            this.commands.setText(line);
        } else {
            this.commands.setText(line + "\n" + this.commands.getText());
        }
    }

    public static void main(String[] args) {
        try {
            try {
                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            } catch (Exception e) {
                System.err.println("Failed to set look and feel");
            }

            Robot robot = new Robot();
            new MouseTurtle(robot);
        } catch (AWTException e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(null, "Sorry your computer is too lame to support turtle commands", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }

}