asked on

NullPointException error don't see it

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
}
}
}
}

ASKER CERTIFIED SOLUTION

Mick Barry

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Mick Barry

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http://www.objects.com.au/staff/mick

Javatm

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

Javatm

Your 2 fast you think you havent seen my solution.

Drop_of_Rain

ASKER

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);
}
}
}
}

twobitadder

jLabel = JLabel();

should be

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

twobitadder

it should be jLabel1 = new jLabel() actually, you don't have any object called jlabel