这里使用了lombok打印日志，也可以不用

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();  
}  
/\*\*  
&nbsp;\* 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  
&nbsp;\*/  
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&nbsp;  
 char c1 = hexDigits\[bt & 0xf\];// 取字节中低 4 位的数字转换&nbsp;  
 stringbuffer.append(c0);  
 stringbuffer.append(c1);  
}  

}