[RESOLVED] simple question of char

[newpat]

char C='e';

C=JOptionPane.showInputDialog("A/B?").charAt(0);
switch(C)
{
	case'A':case'a':
	System.out.print("A");
	break;
	case'B':case'b':
	System.out.print("B");
	break;
	default:
             JOptionPane.showMessageDialog(null, "Please answerA/B.");
	break;
}

But people enter AAA,BBB instead of A,B,and that is ok...But i dun want it
being happen...how to de this bug?