Window.java

package com.vladislav;

// Import libraries for create UI and event
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

// Extends JFrame, contain game's field and realized listen keyboard
public class Window extends JFrame {
    Field field;

    // Listen keyboard and move cup
    private class Key implements KeyListener {
        public void keyPressed(KeyEvent e) {
            int key = e.getKeyCode();

            if (key == 27) {
                // Close window
                System.exit(0);
            } else if (key == 37) {
                // Left
                if (field.x - 30 > -48)
                    field.x -= 30;
                else
                    field.x = 752;
            } else if (key == 39) {
                // Right
                if (field.x + 30 < 752)
                    field.x += 30;
                else
                    field.x = -48;
            }
        }

        public void keyReleased(KeyEvent e) {

        }

        public void keyTyped(KeyEvent e) {

        }
    }

    public Window(int hard) {
        // Create field with hard
        field = new Field(hard);

        // Add listener and set focus
        addKeyListener(new Key());
        setFocusable(true);

        // Add field - main body for drawing
        Container container = getContentPane();
        container.add(field);

        // Set window (bounds, title, visible)
        setBounds(100, 100, 800, 600);
        setTitle("Java Application");
        setVisible(true);
    }
}