Ошибка в коде - Java (241054)

package grow;
 
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.LayoutManager;
import java.awt.Toolkit;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
 
public class Cipher
extends JFrame {
    private JLabel labelOutput;
    private JTextField textFieldInput;
    private JTextField textFieldKey;
    private JTextField textFieldOutput;
    static Cipher app;
 
    public Cipher() {
        super("\u0428\u0438\u0444\u0440");
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        this.setBounds((dim.width - 450) / 2, (dim.height - 250) / 2, 450, 250);
        JLabel labelInput = new JLabel("\u0412\u0432\u0435\u0434\u0438\u0442\u0435 \u0442\u0435\u043a\u0441\u0442:");
        JLabel labelKey = new JLabel("\u0412\u0432\u0435\u0434\u0438\u0442\u0435 \u043a\u043b\u044e\u0447:");
        this.labelOutput = new JLabel("");
        this.textFieldInput = new JTextField(20);
        this.textFieldKey = new JTextField(15);
        this.textFieldOutput = new JTextField(20);
        JButton buttonCode = new JButton("\u0417\u0430\u043a\u043e\u0434\u0438\u0440\u043e\u0432\u0430\u0442\u044c");
        JButton buttonDecode = new JButton("\u0420\u0430\u0441\u043a\u043e\u0434\u0438\u0440\u043e\u0432\u0430\u0442\u044c");
        JButton buttonExit = new JButton("\u0412\u044b\u0445\u043e\u0434");
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints opt = new GridBagConstraints();
        opt.gridx = 0;
        opt.gridy = 0;
        opt.anchor = 17;
        opt.insets = new Insets(5, 5, 5, 5);
        panel.add((Component)labelInput, opt);
        ++opt.gridx;
        panel.add((Component)this.textFieldInput, opt);
        --opt.gridx;
        ++opt.gridy;
        panel.add((Component)labelKey, opt);
        ++opt.gridx;
        panel.add((Component)this.textFieldKey, opt);
        this.labelOutput.setVisible(false);
        this.textFieldOutput.setVisible(false);
        --opt.gridx;
        ++opt.gridy;
        panel.add((Component)this.labelOutput, opt);
        ++opt.gridx;
        panel.add((Component)this.textFieldOutput, opt);
        --opt.gridx;
        ++opt.gridy;
        panel.add((Component)buttonCode, opt);
        ++opt.gridx;
        panel.add((Component)buttonDecode, opt);
        opt.gridwidth = 2;
        opt.anchor = 10;
        --opt.gridx;
        ++opt.gridy;
        panel.add((Component)buttonExit, opt);
        this.add((Component)panel);
        buttonCode.addActionListener((ActionListener)new ButtonCodeListener(this)); 
        buttonDecode.addActionListener((ActionListener)new ButtonDecodeListener(this));
        buttonExit.addActionListener((ActionListener)new ButtonExitListener(this));
        this.setDefaultCloseOperation(3);
    }
 
    public static void main(String[] args) {
        app = new Cipher();
        app.setVisible(true);
    }
 
    static /* synthetic */ JTextField access$0(Cipher cipher) {
        return cipher.textFieldKey;
    }
 
    static /* synthetic */ JTextField access$1(Cipher cipher) {
        return cipher.textFieldInput;
    }
 
    static /* synthetic */ JTextField access$2(Cipher cipher) {
        return cipher.textFieldOutput;
    }
 
    static /* synthetic */ JLabel access$3(Cipher cipher) {
        return cipher.labelOutput;
    }
}

package grow;
 
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
public class ButtonExitListener
implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent arg0) {
        Cipher.this.setVisible(false);
        Cipher.this.dispose();
    }
}