java校验输入的是否是数字还是字母

private static boolean getStringType(String str) {
	  String txt = str + "";
	  Pattern p = ("[0-9]*");
	  Matcher m = (txt);
	  if (()) {// 输入的是数字
	  return true;
	  }
	  p = ("[a-zA-Z]");
	  m = (txt);
	  return false;
   }