Gzip to compress zip files

Question

hi everyone..i am making a backup utility. it will compress, encrypt and split the files and send it to an ftp server. i have everything worked out except for one bug...when i compress already compressed data, it gets corrupted...like installers, or zip and rar files..i cannot retrieve the files after compressing them with the program. here is the code for compressing and decompressing, can anyone help me?
private string CompressFile(string filetocompress)
               try
                    FileInputStream fis = new FileInputStream(filetocompress);          
                    FileOutputStream fos = new FileOutputStream(filetocompress + "test123");          
                    GZIPOutputStream gzos = new GZIPOutputStream(fos);          
                    sbyte[] buffer = new sbyte[2048];          
                    int read = fis.read(buffer);          
                    while (read == 2048)          
                         gzos.write(buffer);               
                         read = fis.read(buffer);          
                    gzos.write(buffer, 0, read);          
                    // The next step is VERY important. If you do not flush the buffer          
                    // on the inner (gzip) stream, the outer (file) stream will get          
                    // closed before it gets the last buffer of data.          
                    gzos.close();          
                    fis.close();          
                    fos.close();
                    return filetocompress + "test123";
               catch (Exception e)
               return filetocompress + "test123";
private string DecompressFile(string filetocompress)
               try
                    GZIPInputStream gin = new GZIPInputStream(new FileInputStream(filetocompress));
                    OutputStream fout = new FileOutputStream(filetocompress + "test1234");
                    // Transfer bytes from the compressed file to the output file
                    sbyte[] buf = new sbyte[1024*1024];
                    int len;
                    while ((len = gin.read(buf)) > 0)
                         fout.write(buf, 0, len);
                         fout.flush();
                    // Close the file and stream
                    gin.close();
                    fout.close();
                    return filetocompress + "test1234";
               catch (Exception e)
               return filetocompress + "test1234";

Answer 1

sbyte[] buffer = new sbyte[2048];
Where has sbyte come from? ASAIK java has no signed byte.
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