Solved

NullPointException error don't see it

Posted on 2004-04-02
7
210 Views
Last Modified: 2010-03-31
It happen here:  add(jLabel1);  jLabel1.setText("Defensive Moves"); setBackground(Color.white);




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

public class MyClass4 extends JPanel {
  JLabel jLabel1;  
 
  ArrayList myArrayList = new ArrayList();

// Constructor
public MyClass4() {

    setLayout(new GridLayout(0,3)); // Setting MY layout...

add(jLabel1);  jLabel1.setText("Defensive Moves"); setBackground(Color.white);

    looprow:
        for (int row=0; row<20; row++) {
            for(int col=0; col<3; col++) {
                int n=(20*col+row+1);
                if (n>50) break looprow;
                JCheckBox check = new JCheckBox("" + n);

            myArrayList.add(check);
add(check); // Adding it to ME
}
}
}
}
0
Comment
Question by:Drop_of_Rain
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
  • 2
  • +1
7 Comments
 
LVL 92

Accepted Solution

by:
objects earned 100 total points
ID: 10746541
jLabel1 is null.

Change declaration to:
  JLabel jLabel1 = new JLabel();  
0
 
LVL 92

Expert Comment

by:objects
ID: 10746586
0
 
LVL 15

Expert Comment

by:Javatm
ID: 10746589
Friend;

You need to also call the jLabel after you had declared it like :

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

public class MyClass4 extends JPanel {

  JLabel jLabel1;  
  ArrayList myArrayList = new ArrayList();

public MyClass4() {

     // Call it like this . . .
    jLabel = JLabel();

    setLayout(new GridLayout(0,3)); // Setting MY layout...
 
    add(jLabel1);  
    jLabel1.setText("Defensive Moves");
    setBackground(Color.white);

    looprow:
    for (int row=0; row<20; row++) {
    for(int col=0; col<3; col++) {
    int n=(20*col+row+1);
    if (n>50) break looprow;
    JCheckBox check = new JCheckBox("" + n);

    myArrayList.add(check);
    add(check);
    }
    }
}
}

Hope that helps . . .
Javatm
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 15

Expert Comment

by:Javatm
ID: 10746614
Your 2 fast you think you havent seen my solution.
0
 

Author Comment

by:Drop_of_Rain
ID: 10746654
Error can't resolve method jLabel1()



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

public class MyClass4 extends JPanel {

  JLabel jLabel1;  
  ArrayList myArrayList = new ArrayList();

public MyClass4() {

     // Call it like this . . .
    jLabel = JLabel();

    setLayout(new GridLayout(0,3)); // Setting MY layout...
 
    add(jLabel1);  
    jLabel1.setText("Defensive Moves");
    setBackground(Color.white);

    looprow:
    for (int row=0; row<20; row++) {
    for(int col=0; col<3; col++) {
    int n=(20*col+row+1);
    if (n>50) break looprow;
    JCheckBox check = new JCheckBox("" + n);

    myArrayList.add(check);
    add(check);
    }
    }
}
}
0
 
LVL 5

Expert Comment

by:twobitadder
ID: 10747819
jLabel = JLabel();

should be

jLabel = new JLabel();   //to initialise a new JLabel you use the new operator.
0
 
LVL 5

Expert Comment

by:twobitadder
ID: 10747824
it should be jLabel1 = new jLabel() actually, you don't have any object called jlabel
0

Featured Post

Enroll in May's Course of the Month

May’s Course of the Month is now available! Experts Exchange’s Premium Members and Team Accounts have access to a complimentary course each month as part of their membership—an extra way to increase training and boost professional development.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

An old method to applying the Singleton pattern in your Java code is to check if a static instance, defined in the same class that needs to be instantiated once and only once, is null and then create a new instance; otherwise, the pre-existing insta…
After being asked a question last year, I went into one of my moods where I did some research and code just for the fun and learning of it all.  Subsequently, from this journey, I put together this article on "Range Searching Using Visual Basic.NET …
Viewers learn about the scanner class in this video and are introduced to receiving user input for their programs. Additionally, objects, conditional statements, and loops are used to help reinforce the concepts. Introduce Scanner class: Importing…
Viewers learn how to read error messages and identify possible mistakes that could cause hours of frustration. Coding is as much about debugging your code as it is about writing it. Define Error Message: Line Numbers: Type of Error: Break Down…
Suggested Courses

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question