code: public static String trim(CharSequence cs) {
          if (null == cs)
              return null;
          int length = cs.length();
          if (length == 0)
              return cs.toString();
          int l = 0;
          int last = length - 1;
          int r = last;
          for (; l < length; l++) {
              if (!Character.isWhitespace(cs.charAt(l)))
                  break;
          }
          for (; r > l; r--) {
              if (!Character.isWhitespace(cs.charAt(r)))
                  break;
          }
          if (l > r)
              return "";
          else if (l == 0 && r == last)
              return cs.toString();
          return cs.subSequence(l, r + 1).toString();
      }
docs: 去掉字符串前后空白字符。空白字符的定义由Character.isWhitespace来判断
  
  @param cs
  字符串
  @return 去掉了前后空白字符的新字符串