public static byte[] createChecksum(String filename) throws Exception {
InputStream fis = new FileInputStream(filename); //将流类型字符串转换为String类型字符串
byte[] buffer = new byte[1024];
MessageDigest complete = ("MD5"); //如果想使用SHA-1或SHA-256，则传入SHA-1,SHA-256
int numRead;
do {
numRead = (buffer); //从文件读到buffer，最多装满buffer
if (numRead > 0) {
(buffer, 0, numRead); //用读到的字节进行MD5的计算，第二个参数是偏移量
}
} while (numRead != -1);
();
return ();
}
public static String getMD5Checksum(String filename) throws Exception {
byte[] b = createChecksum(filename);
String result = "";
for (int i=0; i < ; i++) {
result += ( ( b[i] & 0xff ) + 0x100, 16).substring(1);//加0x100是因为有的b[i]的十六进制只有1位
}
return result;
}