Intro : This program is supposed to act as a scientific calculator with a basic GUI. An input is mandatory for which a JTextField is used to take input. Then there is a drop-down list with operators. Based on selection of binary (+ , - , * , / , % , ^) operator in JComboBox, the second JTextField has to appear in the frame. For operators like (1/n , n^2 , n^3 , sin , cos , tan , n! , sqrt) the second JTextField is not required.

I have tried to just to hide the field when not required using the .setVisible(False) method and perform the opposite when required.

How do I get this going ?

public void show()
        {
            JFrame frame = new JFrame("Scientific Calculator");
            frame.setPreferredSize(new Dimension(600, 200));
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            JPanel panel = new JPanel();
            JTextField input1 = new JTextField(10);
            JComboBox<String> operator = new JComboBox<String>(
                new String[] { "+", "-", "*", "/", "%", "^", "1/n", "n^2", "n^3", "sin", "cos", "tan", "n!", "sqrt"}
            );
            JTextField input2 = new JTextField(10);
            JButton calcbutton = new JButton("Calculate");
            result = new JLabel("    ");
            result.setBorder(BorderFactory.createLineBorder(Color.BLACK));
            calcbutton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    String s1 = input1.getText();
                    op = operator.getItemAt(operator.getSelectedIndex());
                    if(op == "+" | op == "-" | op == "*" | op == "/" | op == "%" | op == "^")
                    {
                        String s2 = input2.getText();
                        controller.handleUserInput(s1, op, s2);
                    }
                    else if(op == "1/n" | op == "n^2" | op == "n^3" | op == "sin" | op == "cos" | op == "tan" | op == "n!" | op == "sqrt")
                    {
                        controller.handleUserInput(s1, op);
                    }
                }
            });
            panel.add(input1);
            panel.add(operator);
            panel.add(input2).setVisible(false);
            operator.addActionListener(new ActionListener(){
                public void actionPerformed(ActionEvent e){
                    op = e.getSource().toString();
                    if(op == "+" | op == "-" | op == "*" | op == "/" | op == "%" | op == "^")
                    {
                        panel.add(input2).setVisible(true);
                    }
                }
            });
            // panel.add(input2);
            panel.add(calcbutton);
            panel.add(result);
            frame.add(panel);
            frame.pack();
            frame.setVisible(true);
        }