MarvellousPacker.java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Stream;

import javax.swing.event.SwingPropertyChangeSupport;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Arrays;

public class MarvellousPacker
{
    FileOutputStream outstream = null;
    
    String ValidExt[] = {".txt",".c",".java",".cpp"};

    public MarvellousPacker(String src,String Dest) throws Exception
    {
        String Magic = "Marvellous11";
        byte arr[] = Magic.getBytes();
        File outfile = new File(Dest);

        File infile = null;
        outstream = new FileOutputStream(Dest);
        outstream.write(arr,0,arr.length);

        File folder = new File(src);

        System.setProperty("user.dir",src);

        listAllFiles(src);
    }

    public void listAllFiles(String path)
    {
        try
        (Stream<Path> paths = Files.walk(Paths.get(path)))
        {
            paths.forEach(filePath ->
            {
                if (Files.isRegularFile(filePath))
                {
                    try
                    {
                        String name = filePath.getFileName().toString();
                        String ext = name.substring(name.lastIndexOf("."));

                        List<String> list = Arrays.asList(ValidExt);

                        if(list.contains(ext))
                        {
                            File file = new File(filePath.getFileName().toString());
                            Pack(file.getAbsolutePath());
                        }
                    }
                    catch(Exception e)
                    {
                        System.out.println(e);
                    }
                }
            });
            
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
    public void Pack(String filePath)
    {
        FileInputStream instream = null;

        try
        {
            byte[] buffer = new byte[1024];

            int length;

            byte temp[] = new byte[100];

            File fobj = new File(filePath);

            String Header = filePath+" "+fobj.length();

            for(int i = Header.length(); i < 100;i++)
                Header+=" ";
            
            temp = Header.getBytes();

            instream = new FileInputStream(filePath);

            outstream .write(temp,0,temp.length);

            while((length = instream.read(buffer)) > 0)
            {
                outstream.write(buffer,0,length);
            }

            instream.close();
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
}