问如何在Android中为文件生成MD5校验和？

EN

public static String getMD5EncryptedString(String encTarget){
        MessageDigest mdEnc = null;
        try {
            mdEnc = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("Exception while encrypting to md5");
            e.printStackTrace();
        } // Encryption algorithm
        mdEnc.update(encTarget.getBytes(), 0, encTarget.length());
        String md5 = new BigInteger(1, mdEnc.digest()).toString(16);
        while ( md5.length() < 32 ) {
            md5 = "0"+md5;
        }
        return md5;
    }

/*
 * Copyright (C) 2012 The CyanogenMod Project
 *
 * * Licensed under the GNU GPLv2 license
 *
 * The text of the license can be found in the LICENSE file
 * or at https://www.gnu.org/licenses/gpl-2.0.txt
 */

package com.cyanogenmod.updater.utils;

import android.text.TextUtils;
import android.util.Log;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {
    private static final String TAG = "MD5";

    public static boolean checkMD5(String md5, File updateFile) {
        if (TextUtils.isEmpty(md5) || updateFile == null) {
            Log.e(TAG, "MD5 string empty or updateFile null");
            return false;
        }

        String calculatedDigest = calculateMD5(updateFile);
        if (calculatedDigest == null) {
            Log.e(TAG, "calculatedDigest null");
            return false;
        }

        Log.v(TAG, "Calculated digest: " + calculatedDigest);
        Log.v(TAG, "Provided digest: " + md5);

        return calculatedDigest.equalsIgnoreCase(md5);
    }

    public static String calculateMD5(File updateFile) {
        MessageDigest digest;
        try {
            digest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            Log.e(TAG, "Exception while getting digest", e);
            return null;
        }

        InputStream is;
        try {
            is = new FileInputStream(updateFile);
        } catch (FileNotFoundException e) {
            Log.e(TAG, "Exception while getting FileInputStream", e);
            return null;
        }

        byte[] buffer = new byte[8192];
        int read;
        try {
            while ((read = is.read(buffer)) > 0) {
                digest.update(buffer, 0, read);
            }
            byte[] md5sum = digest.digest();
            BigInteger bigInt = new BigInteger(1, md5sum);
            String output = bigInt.toString(16);
            // Fill to 32 chars
            output = String.format("%32s", output).replace(' ', '0');
            return output;
        } catch (IOException e) {
            throw new RuntimeException("Unable to process file for MD5", e);
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                Log.e(TAG, "Exception on closing MD5 input stream", e);
            }
        }
    }
}

public static String fileToMD5(String filePath) {
    InputStream inputStream = null;
    try {
        inputStream = new FileInputStream(filePath);
        byte[] buffer = new byte[1024];
        MessageDigest digest = MessageDigest.getInstance("MD5");
        int numRead = 0;
        while (numRead != -1) {
            numRead = inputStream.read(buffer);
            if (numRead > 0)
                digest.update(buffer, 0, numRead);
        }
        byte [] md5Bytes = digest.digest();
        return convertHashToString(md5Bytes);
    } catch (Exception e) {
        return null;
    } finally {
        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (Exception e) { }
        }
    }
}

private static String convertHashToString(byte[] md5Bytes) {
    String returnVal = "";
    for (int i = 0; i < md5Bytes.length; i++) {
        returnVal += Integer.toString(( md5Bytes[i] & 0xff ) + 0x100, 16).substring(1);
    }
    return returnVal.toUpperCase();
}