EcryptionDecryption

    private void btn_encryptActionPerformed(java.awt.event.ActionEvent evt) {
        char a[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
        int key = Integer.parseInt(tf_key.getText());
        String text = tf_text.getText();
        int k = 25 - key;
        char[] result = new char[text.length()]; // {'t', 'f', 'd', 'v', 's', 'f'}
        char[] letters = text.toLowerCase().toCharArray(); // {'s', 'e', 'c', 'u', 'r', 'e'}
        for (int i = 0; i < text.length(); i++) {
            for (int j = 0; j < a.length; j++) {
                if (j <= k) {
                    if (letters[i] == a[j]) {
                        result[i] = a[j + key];
                    }
                } else {
                    if (letters[i] == a[j]) {
                        result[i] = a[j - (k + 1)];
                    }
                }
            }
        }
        String generatedCipher = String.valueOf(result); // tfdvsfa
        tf_cipher.setText(generatedCipher); // tfdvsfa
    }

    private void btn_decryptActionPerformed(java.awt.event.ActionEvent evt) {
        char a[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
        int key = Integer.parseInt(tf_key.getText());
        String text = tf_text.getText();
        int k = 25 - key;
        char[] result = new char[text.length()];
        char[] letters = text.toLowerCase().toCharArray();
        for (int i = 0; i < text.length(); i++) {
            for (int j = 0; j < a.length; j++) {
                if (j > (key - 1)) {
                    if (letters[i] == a[j]) {
                        result[i] = a[j - key];
                    }
                } else {
                    if (letters[i] == a[j]) {
                        result[i] = a[j + (k + 1)];
                    }
                }
            }
        }
        String generatedCipher = String.valueOf(result);
        tf_cipher.setText(generatedCipher);
    }