EF BB BF UTF-8(可变长1-4字节，兼容ASCII)
FE FF UTF-16/UCS-2, little endian(定长2字节)
FF FE UTF-16/UCS-2, big endian(定长2字节)
FF FE 00 00 UTF-32/UCS-4, little endian(定长4字节)
00 00 FE FF UTF-32/UCS-4, big-endian(定长4字节)
原文：http://www.cnblogs.com/yipeng-yu/p/5478526.html