Question

I’m switching to Java from Python and I’m having a little difficulty with my project. I’m writing a GUI in Swing for some ciphers that I teach. I have two packages in my project – cryptolib and cryptogui. Cryptolib contains all the different ciphers as classes and cryptogui is my GUI.

All of my ciphers are sublcasses of a Cipher class that I defined. Currently, I’m having difficulty using the following class.

package cryptolib;
public class SubstitutionCipher extends Cipher{
... implementation here ...
}

In my GUI class, I define a menu item to switch to the Substitution cipher using an anonymous class.

package cryptogui;
import cryptolib.*;
public class CryptoSwing extends JFrame {
    private Cipher cipher;
    public CryptoSwing() {
        JMenuItem mntmSubstitution = new JMenuItem("Substitution");
        mntmSubstitution.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                cipher = SubstitutionCipher(txtSubKeyword.getText());
             }
        });
 }

The problem I’m running into is that while “private Cipher cipher;” works, the SubstitutionCipher code in the ActionListener gives me the error

The method SubstitutionCipher(String) is undefined for the type new ActionListener(){}

The classes I imported from Swing (java.awt.CardLayout, for example) work perfectly. I know it’s probably something fundamental that I’ve missed, but I’ve searched and can’t seem to find the issue.

Answer 1

cipher = SubstitutionCipher(txtSubKeyword.getText());

should probably be

cipher = new SubstitutionCipher(txtSubKeyword.getText());

Notice the new keyword.