获取字符串已utf-8表示的字节数

 private static int utf8Length(String string) { /** Returns the number of bytes required to write this. */
     int stringLength = string.length();
     int utf8Length = 0;
     for (int i = 0; i < stringLength; i++) {
       int c = string.charAt(i);
       if (c <= 0x007F) {
         utf8Length++;
       } else if (c > 0x07FF) {
         utf8Length += 3;
       } else {
         utf8Length += 2;
       }
     }
     return utf8Length;
   }

当然我们是可以直接使用String.getBytes("utf-8"),但是效率方面肯定不如上面的代码