import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.Color;
import java.awt.event.KeyListener;
import java.awt.event.KeyEvent;
import java.awt.Point;

class Program01 extends JFrame {
	JPanel panel;
	Timer timer;
	enum TDirection {left, right}
	TDirection direction = TDirection.left;
	Program01() {
		timer = new Timer (10, new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				MehetIdozitoActionEvent(e);
			}
		});

		addKeyListener(new KeyListener() {
			public void keyPressed(KeyEvent e) {
				OnKeyPressed(e);
			}
			public void keyReleased(KeyEvent e) {}
			public void keyTyped(KeyEvent e) {}
		});
		panel = new JPanel();
		panel.setBounds(10, 300, 100, 30);
		panel.setBackground(Color.green);

		add(panel);
		setLayout(null);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(500, 400);
		setVisible(true);
	}
	private void MehetIdozitoActionEvent(ActionEvent e) {
		int x = panel.getX();
		int y = panel.getY();
		if(direction == TDirection.left) {
			if(x>0)
				x = x - 3;
		} else {
			int width = getWidth();
			int a = width - panel.getWidth();
			if(x<a)
				x = x + 3;
		}
		panel.setLocation(new Point(x, y));
	}
	private void OnKeyPressed(KeyEvent e) {
		if(e.getKeyCode() == KeyEvent.VK_ENTER) {
			timer.start();
		}
		if(e.getKeyCode() == KeyEvent.VK_RIGHT) {
			direction = TDirection.right;
		}
		if(e.getKeyCode() == KeyEvent.VK_LEFT) {
			direction = TDirection.left;
		}
	}
	public static void main(String args[]) {
		new Program01();
	}
}