Problem in Array of JCheckBox

Question

I am facing a problem with the array of JCheckBox. Without array it works but when I use array it gives NullPointerException. No compile time error. I am using Null Layout. But I need to use the array. How can I solve this?
Here is the code.
JCheckBox jCheckBox_Questions[] = new JCheckBox[3];
JCheckBox box = new JCheckBox();
Dimension d[] = new Dimension[3] ;
String strQuestions[] = {"No Child ?","Jaundice ?","Migraine ?"};
int j=20,k=150;
// This works
box.setText(strQuestions[0]);
add(box);
d[1]= box.getPreferredSize();
box.setBounds(j,k,d[1].width,d[1].height);
k=k+20;
//When I add the follwing fragment it gives NullPointerException
jCheckBox_Questions[0]. setText(strQuestions[1]);// in this line
add(jCheckBox_Questions[0]);
d[2]= jCheckBox_Questions[0].getPreferredSize();
jCheckBox_Questions[0].setBounds(j,k,d[2].width,d[2].height);

Answer 1

Hi,
classic error: in fact the code
   JCheckBox jCheckBox_Questions[] = new JCheckBox[3]; doesn't instantiate the checkboxes, it's only allocating 3 memory pointers (inited to null), ready to receive the futures instances of checkboxes. So you should have typed:
   JCheckBox jCheckBox_Questions[] = new JCheckBox[3];
   // Here we create the 3 objects
   for (int i=0;i<3;i++) jCheckBox_Questions[ i ] = new JCheckBox();
   //...Hope this will help,
Regards.