Can we add a panel in other panel? If yes, then what's wrong in my code

Question

I am trying to make a very simple Time Manager, when i compile it shows an error. I am unable to find the mistake in my code which is producing the error.

JPanel otherPanel = new JPanel();
otherPanel.add(BorderLayout.WEST, timingsPanel);
otherPanel.add(BorderLayout.CENTER, todoPanel);
otherPanel.add(BorderLayout.EAST, checkPanel);

The error is:

Error message: Exception in thread "main" java.lang.NullPointerException
    at java.desktop/java.awt.Container.addImpl(Container.java:1117)
    at java.desktop/java.awt.Container.add(Container.java:460)
    at GUI.setUpGui(GUI.java:57) at manager.main(manager.java:6)

code around line 57:

//setting up otherstuff
otherPanel = new JPanel();
otherPanel.add(BorderLayout.WEST, timingsPanel);
otherPanel.add(BorderLayout.CENTER, todoPanel);
otherPanel.add(BorderLayout.EAST, checkPanel);

The below code in minimum, it's also showing the same error

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

public class timeclass
{
    JFrame frame;
    JPanel headerPanel;
    JLabel header;
    JPanel otherPanel;
    JPanel timingsPanel;
    JPanel todoPanel;
    JPanel checkPanel;


    public void setUpGui()
    {
        frame = new JFrame("Time Manager");

        //setting up header
        headerPanel = new JPanel();
        header = new JLabel("Time Manager");
        header.setFont(new Font("Times New Roman", Font.BOLD, 36));
        headerPanel.add(header);

        //setting up otherstuff
        otherPanel = new JPanel();
        otherPanel.add(BorderLayout.WEST, timingsPanel);
        otherPanel.add(BorderLayout.CENTER, todoPanel);
        otherPanel.add(BorderLayout.EAST, checkPanel);

        //setting up frame
        frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
        BoxLayout boxLayout4 = new BoxLayout(frame, BoxLayout.Y_AXIS);
        frame.setLayout(boxLayout4);
        frame.add(headerPanel);
        frame.add(otherPanel);
        frame.setSize(900, 400);
        frame.setVisible(true);
    }
}

Error message: Exception in thread "main" java.lang.NullPointerException at java.desktop/java.awt.Container.addImpl(Container.java:1117) at java.desktop/java.awt.Container.add(Container.java:460) at GUI.setUpGui(GUI.java:57) at manager.main(manager.java:6) — x blade, Jan 09 '20 at 19:53
One of `timingsPanel`, `todoPanel` or `checkPanel` is `null`. — azurefrog, Jan 09 '20 at 19:55
I would say one of the panels you are trying to add wasn't initialized and your variable is NULL — , Jan 09 '20 at 19:55
It seems that you forgot to create some panel... Please, take a look here https://stackoverflow.com/help/minimal-reproducible-example and here https://stackoverflow.com/help/how-to-ask — davidbuzatto, Jan 09 '20 at 19:55
Whenever you get an NPE, start looking and printing out values to see if they have been properly initialized. It's usually much faster than waiting for help. — WJS, Jan 09 '20 at 19:56
The error could be anywhere. We're not going to be able to find it just by looking at these four lines of code. Can you produce a minimal example that shows the error? — Dawood ibn Kareem, Jan 09 '20 at 20:00
There was dedicated post with houndreds of upvotes as standard "this is duplication" flag that explains "what is nullpointerexception and how to fix it" but for whatever reasons i cannot find that on stackoverflow now. — Antoniossss, Jan 09 '20 at 20:12
The `otherPanel.add(BorderLayout.WEST, timingsPanel);` construct has been obsolete since Java1.1.. — FredK, Jan 09 '20 at 20:35

Can we add a panel in other panel? If yes, then what's wrong in my code

0 Answers0