Java正则表达式判断输入的是否为数字

public static boolean isNumeric(String str)
    {
          Pattern pattern = Pattern.compile("\\d+\\.?\\d+");
          Matcher isNum = pattern.matcher(str);
          if( !isNum.matches() )
          {
        	  System.out.println("not");
                return false;
          }
          System.out.println("yes");
          return true;
    }