JAVA生成文件的md5校验值

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import lombok.extern.slf4j.Slf4j;
/**
* author yvioo
*/
@Slf4j
public class MD5Util {
/**
* 生成文件的md5校验值
* 
* @param path 文件路径
* @return 文件md5校验值
* @throws IOException
* @throws NoSuchAlgorithmException
*/
public static String getFileMD5String(String path){
InputStream fis = null;
MessageDigest messagedigest = null;
try {
messagedigest = MessageDigest.getInstance("md5");
File file = new File(path);
if(!file.exists() || !file.isFile()) {
log.error("不存在或不是一个文件");
return "";
} fis = new FileInputStream(file);
byte[] buffer = new byte[1024];
int numRead = 0;
while ((numRead = fis.read(buffer)) > 0) {
messagedigest.update(buffer, 0, numRead);
}
}catch (IOException e) {
e.printStackTrace();
}catch (NoSuchAlgorithmException e){
e.printStackTrace();
}finally {
try {
if(fis != null) {
fis.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return bufferToHex(messagedigest.digest());
}
private static String bufferToHex(byte bytes[]) {
return bufferToHex(bytes, 0, bytes.length);
}
private static String bufferToHex(byte bytes[], int m, int n) {
StringBuffer stringbuffer = new StringBuffer(2 * n);
int k = m + n;
for (int l = m; l < k; l++) {
appendHexPair(bytes[l], stringbuffer);
}
return stringbuffer.toString();
}
/**
 * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合
 */
protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换, >>> 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同 
char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换 
stringbuffer.append(c0);
stringbuffer.append(c1);
}
}