Java計算文件MD5值代碼

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class FileMd5Utils {
     protected static char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};

        protected static MessageDigest messageDigest = null;

        static{
            try{

                messageDigest = MessageDigest.getInstance("MD5");

            }catch (NoSuchAlgorithmException e) {

                System.err.println(FileMd5Utils.class.getName()+"初始化失敗，MessageDigest不支持MD5Util.");

                e.printStackTrace();

            }

        }

    /** 
     * 計算文件的MD5 
     * @param fileName 文件的絕對路徑 
     * @return 
     * @throws IOException 
     */  
    public static String getFileMD5String(String fileName) throws IOException{  
        File f = new File(fileName);  
        return getFileMD5String(f);  
    }  

    /** 
     * 計算文件的MD5，重載方法 
     * @param file 文件對象 
     * @return 
     * @throws IOException 
     */  
    public static String getFileMD5String(File file) throws IOException{  
        FileInputStream in = new FileInputStream(file);  
        FileChannel ch = in.getChannel();  
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());  
        messageDigest.update(byteBuffer);  
        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();  
    }  

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {  
       char c0 = hexDigits[(bt & 0xf0) >> 4];  
       char c1 = hexDigits[bt & 0xf];  
       stringbuffer.append(c0);  
       stringbuffer.append(c1);  
    }  

    public static void main(String[] args) throws IOException {  
        String fileName = "F:\\test01\\1.txt";
        String str = "d0970714757783e6cf17b26fb8e2298f";
        String str2 = "ea3ed20b6b101a09085ef09c97da1597";
        System.out.println(str.equals(str2));
        System.out.println(getFileMD5String(fileName));
    }  

}
</pre>