文件正确编译，但未显示JFrame

Question

I've been trying for a bit to get this code to work, and I don't know what's wrong with it. Everything I've shown says to declare JFrame properly, but I've already done it and it doesn't appear. Here's my code:

import javax.swing.*;
import java.awt.*;

public class test extends JFrame {

  private JFrame f;
  private JPanel p;
  private JButton b1;
  private JLabel lab;

  public void test() {
    gui();
  }

  public void gui() {
    JFrame f = new JFrame("Frame");
    f.setBounds(30, 30, 700, 1000);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
    f.setFocusable(true);

    p = new JPanel();
    p.setBackground(Color.YELLOW);

    b1 = new JButton("Button");
    lab = new JLabel("Label");

    p.add(b1);
    p.add(lab);

    f.add(p, BorderLayout.SOUTH);
  }

  public static void main(String[] args) {
    new test();
  }
}

I don't understand coding enough to be able to diagnose the problem, so I've come here for assistance. Thank you in advance!

Answer 1

That is because you are not calling the test() method. It seems though that your intention was to make this method a constructor:

  public void test() {
    gui();
  }

It should instead be (constructors don't have a return type):

  public test() {
    gui();
  }

Answer 2

It was a simple mistake. You need a create instance of the class and call the method gui(). You should rename the test to Test. It's best practice.

Answer 3

I made a test object and called test method which was calling gui(); in it.

package vai;
import javax.swing.*;
import java.awt.*;

public class test extends JFrame {

    private JFrame f;
    private JPanel p;
    private JButton b1;
    private JLabel lab;

    public void test() {
      gui();
    }

    public void gui() {
        JFrame f = new JFrame("Frame");
        f.setBounds(30, 30, 700, 1000);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
        f.setFocusable(true);

        p = new JPanel();
        p.setBackground(Color.YELLOW);

        b1 = new JButton("Button");
        lab = new JLabel("Label");

        p.add(b1);
        p.add(lab);

        f.add(p, BorderLayout.SOUTH);
    }

    public static void main(String[] args) {
        test t1 =  new test();
        t1.test();
    }
  }