component

[nasi]

 
import java.awt.FlowLayout;
 
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JCheckBox;
import javax.swing.JComponent;
import javax.swing.JPanel;
import javax.swing.JTextField;
 
public class hyperlikntest extends JComponent{
 
	public static void main(String [] args){
 
		Box f = new Box(BoxLayout.Y_AXIS);
		int NumOfRperP=10;
		JPanel[] p = new JPanel[NumOfRperP];
		JCheckBox[] c = new JCheckBox[NumOfRperP];
		JTextField[] t = new JTextField[NumOfRperP];
 
 
		for (int i =0; i< NumOfRperP; i++){
			t[i].setColumns(50);
			p[i].setLayout(new FlowLayout(FlowLayout.LEFT));
			p[i].add(c[i]);
			p[i].add(t[i]);	
			f.add(p[i]);
		}
 
		f.setVisible(true);
 
	}
 
}

[nasi]

noooooooo answer

[copeg]

noooooooo answer

What is the question?

[nasi]

when I execute the above code it generates :

"Exception in thread "main" java.lang.NullPointerException
at test.hyperlikntest.main(hyperlikntest.java:29)"

I was wondering what is the reason

[copeg]

The code creates an array, but doesn't instantiate the objects of that array

JPanel[] panels = new JPanel[1];
panels[0].add(new JComponent());//throws a null pointer exception because panels[0] was never instantiated
panels[0] = new JPanel();//instantiate
panels[0].add( new JComponent() );//now it works like a charm