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