JTextField not showing up in JPanel on launch

Question

The JTextField is there because when I move the mouse over where it's supposed to be the mouse icon changes to a cursor, then when I click it shows up. But it's invisible at launch. What am I missing?

public class JavaSwingTextfield extends JFrame {
    private static final long serialVersionUID = 1L;

    JTextField myTextField;

    public JavaSwingTextfield(){

        /***** JFrame setup *****/

        // Set the size of the window
        setSize(600,600);

        // Make the application close when the X is clicked on the window
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        // Makes the JFrame visible to the user
        setVisible(true);

        /***** JFrame setup END *****/


        /***** JButton setup *****/

        // Create a JLabel and set its label to "Start"
        myTextField = new JTextField("Start");

        // Set the label's size
        myTextField.setSize(100, 50);

        // Put the label in a certain spot
        myTextField.setLocation(200, 50);

        // Set a font type for the label
        //Font myFont = new Font("Serif", Font.BOLD, 24);
        //myTextField.setFont(myFont);

        // Add the label to the JFrame
        add(myTextField);

        /***** JButton setup END *****/

    }


    /***** The main method *****/
    public static void main(String[] args){ 

        new JavaSwingTextfield();

    }

}

Answer 1

• Use Event Dispatch Thread for creating GUI components
• Do not call setVisible(..) before all components have been added to the JFrame ( this is the above code snippets actual error +1 to @Clark)
• Do not unnecessarily extend JFrame class
• Do not call setSize(..), rather simply call JFrame#pack() before setting the JFrame visible
• Do not call setSize() on JTextField rather look at its constructor: JTextField(String text,int columns)
• Use appropriate LayoutManagers, see here for some examples: A Visual Guide to Layout Managers

Here is an example I made (basically your code with fixes):

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class JavaSwingTextfield {

    private JTextField myTextField;

    public JavaSwingTextfield() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        myTextField = new JTextField("Start");
        
        // Add the label to the JFrame
        frame.add(myTextField);
        
        //pack frame to component preferred sizes
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Create UI on EDT
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new JavaSwingTextfield();
            }
        });
    }
}

Answer 2

You're adding the JTextfield to the JFrame AFTER you've made the JFrame visible. Just add the JTextField before hand.