Can't use imported class in an anonymous class
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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.