Java SE (Java Platform, Standard Edition)

Hi,

Anybody know what exactly means by IllegalArgumentAcception? In my program the error message print out like this:

java.lang.IllegalArgumentException: bad position: 1   at javax.swing.text.JTextComponent.setCaretPosition(JTextComponent.java:1650)

From my coding:

try
     		{
                        String val = "A";
			int pos = getCaretPosition();
  			getDocument().insertString(getCaretPosition(),val,null);
			setCaretPosition(pos+1);
   			moveCaretPosition(pos+1);
			requestFocusInWindow();
     		}catch(Exception input)
     		{ input.printStackTrace(); }

It seems that the

setCaretPosition(pos+1)

in my coding facing problem. But I sure that the coding correct. Is there something out of my sight or something I incorrectly put in there. I need opinion on this matter. Can anybody help?

thanks