Base64,enjoy!

package zte.util;
import java.io.*;       // needed only for main() method.

/**
* 将字符串用64位加密算法加密
* Title:        销售自动化软件
* Description:  实现销售人员能够将销售过程通过一个软件就能管理起来。同时相互之间能够共享信息。
* 兼容以前的ACT,OUTLOOK软件。
* 与OFFICE软件集成。
* Copyright:    Copyright (c) 2001
* Company:      TCL企业软件有限责任公司
* @author       TONY.郑
* @date         17 March 2000
* @version      1.0
*/

//////////////////////license & copyright header/////////////////////////
//                                                                     //
//    Base64 - encode/decode data using the Base64 encoding scheme     //
//                                                                     //
//                Copyright (c) 1998 by Kevin Kelley                   //
//                                                                     //
// This library is free software; you can redistribute it and/or       //
// modify it under the terms of the GNU Lesser General Public          //
// License as published by the Free Software Foundation; either        //
// version 2.1 of the License, or (at your option) any later version.  //
//                                                                     //
// This library is distributed in the hope that it will be useful,     //
// but WITHOUT ANY WARRANTY; without even the implied warranty of      //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the       //
// GNU Lesser General Public License for more details.                 //
//                                                                     //
// You should have received a copy of the GNU Lesser General Public    //
// License along with this library; if not, write to the Free Software //
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA           //
// 02111-1307, USA, or contact the author:                             //
//                                                                     //
// Kevin Kelley <kelley@rura.net.net> - 30718 Rd. 28, La Junta, CO,    //
// 81050  USA.                                                         //
//                                                                     //
////////////////////end license & copyright header///////////////////////


import java.io.*;       // needed only for main() method.


/**
* Provides encoding of raw bytes to base64-encoded characters, and
* decoding of base64 characters to raw bytes.
* 用于加密算法，64位加密软件
* @author Kevin Kelley (kelley@ruralnet.net)
* @version 1.3
* @date 06 August 1998
* @modified 14 February 2000
* @modified 22 September 2000
*/

public class Base64 {

/**
* returns an array of base64-encoded characters to represent the
* passed data array.
*
* @param data the array of bytes to encode
* @return base64-coded character array.
*/
static public char[] encode(byte[] data)
{
    char[] out = new char[((data.length + 2) / 3) * 4];

    //
    // 3 bytes encode to 4 chars.  Output is always an even
    // multiple of 4 characters.
    //
    for (int i=0, index=0; i<data.length; i+=3, index+=4) {
        boolean quad = false;
        boolean trip = false;

        int val = (0xFF & (int) data[i]);
        val <<= 8;
        if ((i+1) < data.length) {
            val |= (0xFF & (int) data[i+1]);
            trip = true;
        }
        val <<= 8;
        if ((i+2) < data.length) {
            val |= (0xFF & (int) data[i+2]);
            quad = true;
        }
        out[index+3] = alphabet[(quad? (val & 0x3F): 64)];
        val >>= 6;
        out[index+2] = alphabet[(trip? (val & 0x3F): 64)];
        val >>= 6;
        out[index+1] = alphabet[val & 0x3F];
        val >>= 6;
        out[index+0] = alphabet[val & 0x3F];
    }
    return out;
}

  /**
   * Decodes a BASE-64 encoded stream to recover the original
   * data. White space before and after will be trimmed away,
   * but no other manipulation of the input will be performed.
   *
   * As of version 1.2 this method will properly handle input
   * containing junk characters (newlines and the like) rather
   * than throwing an error. It does this by pre-parsing the
   * input and generating from that a count of VALID input
   * characters.
   **/
static public byte[] decode(char[] data)
{
    // as our input could contain non-BASE64 data (newlines,
    // whitespace of any sort, whatever) we must first adjust
    // our count of USABLE data so that...
    // (a) we don@#t misallocate the output array, and
    // (b) think that we miscalculated our data length
    //     just because of extraneous throw-away junk

    int tempLen = data.length;
    for( int ix=0; ix<data.length; ix++ )
    {
        if( (data[ix] > 255) || codes[ data[ix] ] < 0 )
            --tempLen;  // ignore non-valid chars and padding
    }
    // calculate required length:
    //  -- 3 bytes for every 4 valid base64 chars
    //  -- plus 2 bytes if there are 3 extra base64 chars,
    //     or plus 1 byte if there are 2 extra.

    int len = (tempLen / 4) * 3;
    if ((tempLen % 4) == 3) len += 2;
    if ((tempLen % 4) == 2) len += 1;

    byte[] out = new byte[len];



    int shift = 0;   // # of excess bits stored in aclearcase/" target="_blank" >ccum
    int accum = 0;   // excess bits
    int index = 0;

    // we now go through the entire array (NOT using the @#tempLen@# value)
    for (int ix=0; ix<data.length; ix++)
    {
        int value = (data[ix]>255)? -1: codes[ data[ix] ];

        if ( value >= 0 )           // skip over non-code
        {
            accum <<= 6;            // bits shift up by 6 each time thru
            shift += 6;             // loop, with new bits being put in
            accum |= value;         // at the bottom.
            if ( shift >= 8 )       // whenever there are 8 or more shifted in,
            {
                shift -= 8;         // write them out (from the top, leaving any
                out[index++] =      // excess at the bottom for next iteration.
                    (byte) ((accum >> shift) & 0xff);
            }
        }
        // we will also have skipped processing a padding null byte (@#=@#) here;
        // these are used ONLY for padding to an even length and do not legally
        // occur as encoded data. for this reason we can ignore the fact that
        // no index++ operation occurs in that special case: the out[] array is
        // initialized to all-zero bytes to start with and that works to our
        // advantage in this combination.
    }

    // if there is STILL something wrong we just have to throw up now!
    if( index != out.length)
    {
        throw new Error("Miscalculated data length (wrote " + index + " instead of " + out.length + ")");
    }

    return out;
}


//
// code characters for values 0..63
//
static private char[] alphabet =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
        .toCharArray();

//
// lookup table for converting base64 characters to value in range 0..63
//
static private byte[] codes = new byte[256];
static {
    for (int i=0; i<256; i++) codes[i] = -1;
    for (int i = @#A@#; i <= @#Z@#; i++) codes[i] = (byte)(     i - @#A@#);
    for (int i = @#a@#; i <= @#z@#; i++) codes[i] = (byte)(26 + i - @#a@#);
    for (int i = @#0@#; i <= @#9@#; i++) codes[i] = (byte)(52 + i - @#0@#);
    codes[@#+@#] = 62;
    codes[@#/@#] = 63;
}




///////////////////////////////////////////////////
// remainder (main method and helper functions) is
// for testing purposes only, feel free to clip it.
///////////////////////////////////////////////////

public static void main(String[] args)
{
    boolean decode = false;

    if (args.length == 0) {
        System.out.println("usage:  java Base64 [-d[ecode]] filename");
        System.exit(0);
    }
    for (int i=0; i<args.length; i++) {
        if ("-decode".equalsIgnoreCase(args[i])) decode = true;
        else if ("-d".equalsIgnoreCase(args[i])) decode = true;
    }

    String filename = args[args.length-1];
    File file = new File(filename);
    if (!file.exists()) {
        System.out.println("Error:  file @#" + filename + "@# doesn@#t exist!");
        System.exit(0);
    }

    if (decode)
    {
        char[] encoded = readChars(file);
        byte[] decoded = decode(encoded);
        writeBytes(file, decoded);
    }
    else
    {
        byte[] decoded = readBytes(file);
        char[] encoded = encode(decoded);
        writeChars(file, encoded);
    }
}

private static byte[] readBytes(File file)
{
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    try
    {
        InputStream fis = new FileInputStream(file);
        InputStream is = new BufferedInputStream(fis);
        int count = 0;
        byte[] buf = new byte[16384];
        while ((count=is.read(buf)) != -1) {
            if (count > 0) baos.write(buf, 0, count);
        }
        is.close();
    }
    catch (Exception e) { e.printStackTrace(); }

    return baos.toByteArray();
}

private static char[] readChars(File file)
{
    CharArrayWriter caw = new CharArrayWriter();
    try
    {
        Reader fr = new FileReader(file);
        Reader in = new BufferedReader(fr);
        int count = 0;
        char[] buf = new char[16384];
        while ((count=in.read(buf)) != -1) {
            if (count > 0) caw.write(buf, 0, count);
        }
        in.close();
    }
    catch (Exception e) { e.printStackTrace(); }

    return caw.toCharArray();
}

private static void writeBytes(File file, byte[] data) {
    try {
        OutputStream fos = new FileOutputStream(file);
        OutputStream os = new BufferedOutputStream(fos);
        os.write(data);
        os.close();
    }
    catch (Exception e) { e.printStackTrace(); }
}

private static void writeChars(File file, char[] data) {
    try {
        Writer fos = new FileWriter(file);
        Writer os = new BufferedWriter(fos);
        os.write(data);
        os.close();
    }
    catch (Exception e) { e.printStackTrace(); }
}
///////////////////////////////////////////////////
// end of test code.
///////////////////////////////////////////////////

}

原文转自：http://www.ltesting.net