Question

I am new to java and i am working on a basic chess game, currently i am working on the player names screen, and i can’t figure out how to hide my jPanel. I get an error saying that it cannot find a symbol here is the code:

package chess;

import java.awt.Color;


public class ChessUI extends javax.swing.JFrame {

    public String pOneName;
    public String pTwoName;

    public ChessUI() {
        initComponents();
        getContentPane().setBackground(Color.white); 
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        playerOneNameText = new javax.swing.JTextField();
        playerTwoNameText = new javax.swing.JTextField();
        playButton = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        errorText = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel2.setText("Player One Name:");

        jLabel3.setText("Player Two Name:");

        playerOneNameText.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                playerOneNameTextActionPerformed(evt);
            }
        });

        playerTwoNameText.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                playerTwoNameTextActionPerformed(evt);
            }
        });

        playButton.setText("Play");
        playButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                playButtonMouseClicked(evt);
            }
        });

        pack();
    }// </editor-fold>

    private void playerOneNameTextActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
    }

    private void playerTwoNameTextActionPerformed(java.awt.event.ActionEvent evt) {

    }

    private void playButtonMouseClicked(java.awt.event.MouseEvent evt) {
        if (playerOneNameText.getText().equals(""))
        {
            errorText.setText("One or More Player Names Missing !");
        }

        if (playerTwoNameText.getText().equals(""))
        {
            errorText.setText("One or More Player Names Missing !");
        }

        pOneName = playerOneNameText.getText();
        pTwoName = playerTwoNameText.getText();

        ChessUI.setVisibile(false); //Error Here


    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(ChessUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ChessUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ChessUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ChessUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new ChessUI().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JLabel errorText;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JButton playButton;
    private javax.swing.JTextField playerOneNameText;
    private javax.swing.JTextField playerTwoNameText;
    // End of variables declaration
}

The error that I get is: non static method setVisible(boolean) cannot be referenced from a static context

Answer 1

ChessUI.setVisibile(false) is reference to the Class not the Object.

The Class describes an instance of an Object.

In order to invoke a (non-static) method on Class, you must reference the instance of that Class (ie the Object).

In your case, simply calling setVisible(false) should work.

While this probably sounds confusing, think of it this way. What would happen if you had two instances of ChessUI? How would you distinguish between them?