java.lang.NullPointerExpectation:null (in java.awt.Container) when adding a JPanel

[Freshtilldeath0]

Hi i am having an issue with this error "java.lang.NullPointerExpectation:null (in java.awt.Container)", it wasn't happening until i added the jpanel any solutions?

package folderCreating;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
 
public class window extends JFrame{
 
    private JTextField textField1;
    private JButton button1;
    private JTextField textField2;
    private JButton button2;
    private JButton button3;
    private JButton button4;
    public static String fileInput;
    public static String folderInput;
 
    public window(){
 
        super("File and Folder Manager");  
 
        setLayout(new FlowLayout());
 
        JPanel p1 = new JPanel();
 
        p1.add(textField1);
        p1.add(button2);
        add(p1);
 
        textField2 = new JTextField(20);
        add(textField2);
 
        button1 = new JButton("Create Folder");
        add(button1);
 
        textField1 = new JTextField(20);
        add(textField1);
 
        button2 = new JButton("Create File");
        add(button2);
}

[arieltal]

which line produces the error?

[jps]

Step through the code as the computer would. First call the constructor:
public window(){
so far so good. continue...
setLayout(new FlowLayout());
JPanel p1 = new JPanel();
ok.... go on.......
p1.add(textField1);
Stop. textField1 has not been initialized. (can not add 'null' to a JPanel)
textField1 must have been assigned a value first. This is not the only variable with the problem.

[arieltal]

well according to your code the compiler is right, you have not initialized the variable textField1,
you need to create a new object with the new keyword, and then you can add it.
edit : the order of which is important, first make object, then add it.