Base 64

[blinkago]

Questo algoritmo fa un po' pena, però ti fa capire abbastanza come funge il tutto!!
ps: produce un'errore negli ultimi bytes

import java.io.*;

public class Base64Decoding {
	StringBuffer buf;
	StringBuffer buf2;
	String Source;
	FileInputStream FileI;
	BufferedInputStream Bis;
	FileOutputStream FileO;
	DataOutputStream Bos;

	public static void main(String[] args) {
		Base64Decoding bas = new Base64Decoding("E:\\e.txt"); 
	}

	public Base64Decoding(String source) {
		Source = source;
		leggi();
		traduci();
		scrivi();
	}
	
	public void scrivi(){
		boolean ela=false;
		int half=0;
		int half2=0;
		int tem=0;
		String temp;
		try {
			FileO = new FileOutputStream(Source+".ex_");
			Bos = new DataOutputStream(FileO);
		for (int i = 0; i < buf2.length()-4; i=i+4) {
			temp=buf2.substring(i,i+4);
			if((temp.compareTo("0000"))==0){
				tem=0x0;
			}else if(temp.compareTo("0001")==0){
				tem=0x1;
			}else if(temp.compareTo("0010")==0){
				tem=0x2;
			}else if(temp.compareTo("0011")==0){
				tem=0x3;
			}else if(temp.compareTo("0100")==0){
				tem=0x4;
			}else if(temp.compareTo("0101")==0){
				tem=0x5;
			}else if(temp.compareTo("0110")==0){
				tem=0x6;
			}else if(temp.compareTo("0111")==0){
				tem=0x7;
			}else if(temp.compareTo("1000")==0){
				tem=0x8;
			}else if(temp.compareTo("1001")==0){
				tem=0x9;
			}else if(temp.compareTo("1010")==0){
				tem=0xa;
			}else if(temp.compareTo("1011")==0){
				tem=0xb;
			}else if(temp.compareTo("1100")==0){
				tem=0xc;
			}else if(temp.compareTo("1101")==0){
				tem=0xd;
			}else if(temp.compareTo("1110")==0){
				tem=0xe;
			}else if(temp.compareTo("1111")==0){
				tem=0xf;
			}
			if(ela==false){
				half=tem;
				tem=0;
				ela=true;
			}else{
				half2=tem;
				tem=0;
				ela=false;
				int finale=(half*0x10)+half2;
				Bos.writeByte(finale);
				half=0;
				half2=0;
			}
			
		}
		Bos.flush();
		Bos.close();
		
		} catch(Exception e) {
			System.err.println(e.toString());
			e.printStackTrace();
		}
	}

	public void leggi() {
		try {
			FileI = new FileInputStream(Source);
			Bis = new BufferedInputStream(FileI);
			buf = new StringBuffer();
			int i = 0;
			do {
				i = Bis.read();
				if ((i != -1) && ((char) i != '\r') && ((char) i != '\n')) {
					buf.append((char) i);
				}
			} while (i != -1);
		} catch (Exception e) {
			System.err.println(e.toString());
			e.printStackTrace();
		}
//		System.out.println("" + buf);
	}

	public void traduci() {
		int a = 0;
		buf2 = new StringBuffer();
		for (int i = 0; i < buf.length(); i++) {
			switch (buf.charAt(i)) {
				case 'A' :
					buf2.append("000000");
					break;
				case 'B' :
					buf2.append("000001");
					break;
				case 'C' :
					buf2.append("000010");
					break;
				case 'D' :
					buf2.append("000011");
					break;
				case 'E' :
					buf2.append("000100");
					break;
				case 'F' :
					buf2.append("000101");
					break;
				case 'G' :
					buf2.append("000110");
					break;
				case 'H' :
					buf2.append("000111");
					break;
				case 'I' :
					buf2.append("001000");
					break;
				case 'J' :
					buf2.append("001001");
					break;
				case 'K' :
					buf2.append("001010");
					break;
				case 'L' :
					buf2.append("001011");
					break;
				case 'M' :
					buf2.append("001100");
					break;
				case 'N' :
					buf2.append("001101");
					break;
				case 'O' :
					buf2.append("001110");
					break;
				case 'P' :
					buf2.append("001111");
					break;
				case 'Q' :
					buf2.append("010000");
					break;
				case 'R' :
					buf2.append("010001");
					break;
				case 'S' :
					buf2.append("010010");
					break;
				case 'T' :
					buf2.append("010011");
					break;
				case 'U' :
					buf2.append("010100");
					break;
				case 'V' :
					buf2.append("010101");
					break;
				case 'W' :
					buf2.append("010110");
					break;
				case 'X' :
					buf2.append("010111");
					break;					
				case 'Y' :
					buf2.append("011000");
					break;
				case 'Z' :
					buf2.append("011001");
					break;
				case 'a' :
					buf2.append("011010");
					break;
				case 'b' :
					buf2.append("011011");
					break;
				case 'c' :
					buf2.append("011100");
					break;
				case 'd' :
					buf2.append("011101");
					break;
				case 'e' :
					buf2.append("011110");
					break;
				case 'f' :
					buf2.append("011111");
					break;
				case 'g' :
					buf2.append("100000");
					break;
				case 'h' :
					buf2.append("100001");
					break;
				case 'i' :
					buf2.append("100010");
					break;
				case 'j' :
					buf2.append("100011");
					break;
				case 'k' :
					buf2.append("100100");
					break;
				case 'l' :
					buf2.append("100101");
					break;
				case 'm' :
					buf2.append("100110");
					break;
				case 'n' :
					buf2.append("100111");
					break;
				case 'o' :
					buf2.append("101000");
					break;
				case 'p' :
					buf2.append("101001");
					break;
				case 'q' :
					buf2.append("101010");
					break;
				case 'r' :
					buf2.append("101011");
					break;
				case 's' :
					buf2.append("101100");
					break;
				case 't' :
					buf2.append("101101");
					break;
				case 'u' :
					buf2.append("101110");
					break;
				case 'v' :
					buf2.append("101111");
					break;
				case 'w' :
					buf2.append("110000");
					break;
				case 'x' :
					buf2.append("110001");
					break;
				case 'y' :
					buf2.append("110010");
					break;
				case 'z' :
					buf2.append("110011");
					break;
				case '0' :
					buf2.append("110100");
					break;
				case '1' :
					buf2.append("110101");
					break;
				case '2' :
					buf2.append("110110");
					break;
				case '3' :
					buf2.append("110111");
					break;
				case '4' :
					buf2.append("111000");
					break;
				case '5' :
					buf2.append("111001");
					break;
				case '6' :
					buf2.append("111010");
					break;
				case '7' :
					buf2.append("111011");
					break;
				case '8' :
					buf2.append("111100");
					break;
				case '9' :
					buf2.append("111101");
					break;
				case '+' :
					buf2.append("111110");
					break;
				case '/' :
					buf2.append("111111");
					break;
				case '=' :
					a++;
					break;
			}
			if(a==1){
				buf2.delete((buf2.length()-2),buf2.length());
			}else if (a==2){
				buf2.delete((buf2.length()-4),buf2.length());
			}
		}
	}
}