PressButtonToOrder

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

class MainFrame extends JFrame {
  private static final long serialVersionUID = 1L;
  private List<NumberdButton> numbers = new ArrayList<NumberdButton>();
  private GridLayout grid = new GridLayout(5, 5);
  private boolean[] pressed = new boolean[5 * 5 + 1];

  public MainFrame(String name) {
    super(name);
    setResizable(false);
  }

  public void setButtons(final Container pane) {
    initPressed();
    initNumbers();
    final JPanel p = new JPanel(grid);
    for (final NumberdButton b : numbers) {
      p.add(b);
      b.addMouseListener(new MouseAdapter() {
        @Override
        public void mouseClicked(MouseEvent e) {
          if (pressed[b.getNumber() - 1]) {
            b.setBackground(Color.BLACK);
            b.setEnabled(false);
            pressed[b.getNumber()] = true;
          }
        }
      });
    }
    pane.add(p, BorderLayout.CENTER);
  }

  private void initNumbers() {
    for (int i = 1; i < 26; i++) {
      numbers.add(new NumberdButton(i));
    }
    Collections.shuffle(numbers);
  }

  private void initPressed() {
    for (int i = 0; i < pressed.length; i++)
      pressed[i] = false;
    pressed[0] = true;
  }

  public static void create(String name) {
    MainFrame frame = new MainFrame(name);
    frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    frame.setButtons(frame.getContentPane());
    frame.pack();
    frame.setVisible(true);
  }
}

class NumberdButton extends JButton {
  private static final long serialVersionUID = 1L;
  private final int number;

  public NumberdButton(int number) {
    super("" + number);
    this.number = number;
  }

  public int getNumber() {
    return number;
  }
}

public class PressButtonToOrder {
  public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        MainFrame.create("PressButtonToOrder");
      }
    });
  }
}