How to set the color of JButtons in an array in java?

Question

Suppose there is an array of the name buttons:
private JButton buttons[] = new JButton[9];
How can I set the color of all the buttons in this array to blue?

This is my entire code: It is a game of Tic Tac Toe with the use of buttons.

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

public class TicTacToe implements ActionListener {
private JButton buttons[] = new JButton[9];
private JFrame window = new JFrame("Tic Tac Toe");
private boolean win = false;
private int count = 0;
private int Xwins = 0, Owins = 0;
private String letter = "";
private int[][] winCombinations = new int[][] {
        {0, 1, 2}, {3, 4, 5}, {6, 7, 8}, //horizontal wins
        {0, 3, 6}, {1, 4, 7}, {2, 5, 8}, //vertical wins
        {0, 4, 8}, {2, 4, 6}                     //diagonal wins
};
String name1 = JOptionPane.showInputDialog("Please enter first player's name");
String name2 = JOptionPane.showInputDialog("Please enter second player's name");

public TicTacToe(){
    JOptionPane.showMessageDialog(null,"Remember Player 1 is X and Player 2 is O.");
    window.setSize(300,300);
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setLayout(new GridLayout(3,3));
    window.setVisible(true);


      for(int i=0; i<=8; i++){
          buttons[i] = new JButton();
          window.add(buttons[i]);
          buttons[i].addActionListener(this);
          buttons[i].setBackground(Color.MAGENTA);
  }
      for (JButton button: buttons) {
           button.setBackground(Color.BLUE);
        }

}

public void actionPerformed(ActionEvent event) {
        count++;
        if(count % 2 == 0){
            letter = "O";

        }else{
            letter = "X";
        }
         JButton pressedButton = (JButton)event.getSource(); 
         pressedButton.setText(letter);
         pressedButton.setEnabled(false);
         pressedButton.setBackground(Color.WHITE);


    //Determine who won
    for(int i=0; i<=7; i++){
        if( buttons[winCombinations[i][0]].getText().equals(buttons[winCombinations[i][1]].getText()) && 
                buttons[winCombinations[i][1]].getText().equals(buttons[winCombinations[i][2]].getText()) && 
                buttons[winCombinations[i][0]].getText() != ""){
                win = true;
            }
        }
        if(win == true){
            if(letter == "X"){
                JOptionPane.showMessageDialog(null, name1 + " wins the game!");
            }else{
                JOptionPane.showMessageDialog(null, name2 + " wins the game!");
            }
            playAgain();
        }else if(count == 9 && win == false){
            JOptionPane.showMessageDialog(null, "The game is tied!");
            playAgain();
        }
    } 

public void playAgain(){
    if(letter == "X"){
        Xwins++;
    }else{
        Owins++;
    }
    JOptionPane.showMessageDialog(null, name1 + " has won this many times: " + Xwins);
    JOptionPane.showMessageDialog(null, name2 + " has won this many times: " + Owins);
    int response = JOptionPane.showConfirmDialog(null, "Would you like to play again?", "Confirm", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);

    if(response == JOptionPane.YES_OPTION){
        reset();
    }else{
        System.exit(0);
    }
}

  public void reset() {
      for(int i = 0; i<=8; i++) {
              buttons[i].setText("");
              buttons[i].setEnabled(true); 
      }
      win = false;
      count = 0;
  }  

public static void main(String[] args){
    TicTacToe play = new TicTacToe();
   }
}

Answer 1

This is actually a sideffect of the JButton .

The background and content are two different concepts. While you can change the background color, it may not change the content area of the button. In fact, it may act differently under different look and feels.

Instead, use JLabel , it's much easier to control...

public class TicTacToe implements ActionListener {

    private JLabel labels[] = new JLabel[9];
    private JFrame window = new JFrame("Tic Tac Toe");
    private boolean win = false;
    private int count = 0;
    private int Xwins = 0, Owins = 0;
    private String letter = "";
    private int[][] winCombinations = new int[][]{
        {0, 1, 2}, {3, 4, 5}, {6, 7, 8}, //horizontal wins
        {0, 3, 6}, {1, 4, 7}, {2, 5, 8}, //vertical wins
        {0, 4, 8}, {2, 4, 6} //diagonal wins
    };
    String name1 = JOptionPane.showInputDialog("Please enter first player's name");
    String name2 = JOptionPane.showInputDialog("Please enter second player's name");

    public TicTacToe() {
        JOptionPane.showMessageDialog(null, "Remember Player 1 is X and Player 2 is O.");
        window.setSize(300, 300);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setLayout(new GridLayout(3, 3));
        window.setVisible(true);

        MouseHandler handler = new MouseHandler();

        for (int i = 0; i <= 8; i++) {
            labels[i] = new JLabel();
            labels[i].setOpaque(true);
            labels[i].setBorder(new LineBorder(Color.LIGHT_GRAY));
            labels[i].setHorizontalAlignment(JLabel.CENTER);
            window.add(labels[i]);
            labels[i].addMouseListener(handler);
            labels[i].setBackground(Color.MAGENTA);
        }
//        for (JButton button : buttons) {
//            button.setBackground(Color.BLUE);
//        }

    }

    public void actionPerformed(ActionEvent event) {
    }

    public void playAgain() {
        if (letter == "X") {
            Xwins++;
        } else {
            Owins++;
        }
        JOptionPane.showMessageDialog(null, name1 + " has won this many times: " + Xwins);
        JOptionPane.showMessageDialog(null, name2 + " has won this many times: " + Owins);
        int response = JOptionPane.showConfirmDialog(null, "Would you like to play again?", "Confirm", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);

        if (response == JOptionPane.YES_OPTION) {
            reset();
        } else {
            System.exit(0);
        }
    }

    public void reset() {
        for (int i = 0; i <= 8; i++) {
            labels[i].setText("");
            labels[i].setEnabled(true);
        }
        win = false;
        count = 0;
    }

    public class MouseHandler extends MouseAdapter {

        @Override
        public void mouseClicked(MouseEvent event) {
            count++;
            if (count % 2 == 0) {
                letter = "O";

            } else {
                letter = "X";
            }
            JLabel pressedLabel = (JLabel) event.getSource();
            pressedLabel.setText(letter);
            pressedLabel.setEnabled(false);
            pressedLabel.setBackground(Color.WHITE);


            //Determine who won
            for (int i = 0; i <= 7; i++) {
                if (labels[winCombinations[i][0]].getText().equals(labels[winCombinations[i][1]].getText())
                                && labels[winCombinations[i][1]].getText().equals(labels[winCombinations[i][2]].getText())
                                && labels[winCombinations[i][0]].getText() != "") {
                    win = true;
                }
            }
            if (win == true) {
                if (letter == "X") {
                    JOptionPane.showMessageDialog(null, name1 + " wins the game!");
                } else {
                    JOptionPane.showMessageDialog(null, name2 + " wins the game!");
                }
                playAgain();
            } else if (count == 9 && win == false) {
                JOptionPane.showMessageDialog(null, "The game is tied!");
                playAgain();
            }
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception ex) {
                }

                TicTacToe play = new TicTacToe();
            }
        });
    }
}

The only other choice you might have is to create an implementation of the button that is capable of only painting the background color, this would require you to extend from AbstractButton , but to be honest, that's a lot of work...

Answer 2

You need to reset the button color to blue in the reset method's for loop:

buttons[i].setBackground(Color.blue);

Here's what the resulting application looks like on my machine and a Mac OSX machine. The buttons change to white after being selected:

If you're on Mac OSX, you may also be having problems with the system Look & Feel. You can change this in your main method like this:

public static void main(String[] args){
   try {
      // Set cross-platform Java L&F (also called "Metal")
      UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
      // alternatively, the following should load the default L&F for your system
      //UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
   } catch (Exception e) {}

   TicTacToe play = new TicTacToe();
}

Answer 3

@808sound is on the right track - some of the standard look and feels (eg Windows) make it weird /hard / difficult to change the color of buttons.

At the start of your program, try setting the LAF via

UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName()); 

More details here