[matt]

I'm not really a fan of GUI's since I might write code to do something once and then never use it again so I write the most simplistic thing to get the job done, and if I need anything changed I just edit the code. :p So here's my interpretation of a simple file packer using GZIP compression.

Packer
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Code

import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.zip.GZIPOutputStream;
import javax.swing.filechooser.FileSystemView;

public class PackGZip {
    
    private static final File packDir, fileCache;
    
    static {
        packDir = new File(FileSystemView.getFileSystemView().getHomeDirectory(), "HF"); //this is the directory of the files it will compress
        fileCache = new File(packDir, "howbow.dat"); //this is the file it will compress to
    }

    public static void compressContents() {
        if(!packDir.exists()) {
            System.out.println("Packing directory does not exist!");
            return;
        }
        File[] datFiles = packDir.listFiles(f -> {
            //write your own custom file filter if you'd like
            return f.isFile();
        });
        try (GZIPOutputStream gzos = new GZIPOutputStream(new FileOutputStream(fileCache)); DataOutputStream dataFile = new DataOutputStream(gzos)) {
            dataFile.writeInt(datFiles.length);
            System.out.println("Appending " + datFiles.length + " entries to config");
            for (File f : datFiles) {
                int length = (int) f.length();
                dataFile.writeInt(length);
                String name = f.getName();
                dataFile.writeUTF(name);
                System.out.println(String.format("Appending to config bytes=%d name=%s", length, name));
                byte[] data = readFile(f);
                dataFile.write(data);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static byte[] readFile(File file) {
        try {
            Path path = Paths.get(file.getAbsolutePath());
            byte[] data = Files.readAllBytes(path);
            return data;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    public static void main(String[] args) {
        compressContents();
    }
}

Unpacker
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Code

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
import javax.swing.filechooser.FileSystemView;

public class UnpackGZip {
    
    private static final File unpackDir, fileCache;
    
    static {
        unpackDir = new File(FileSystemView.getFileSystemView().getHomeDirectory(), "HF"); //this is the folder the compressed file will be extracted to
        fileCache = new File(unpackDir, "howbow.dat"); //this is the compressed file
    }

    public static void decompressContents() {
        if(!unpackDir.exists() || !fileCache.exists()) {
            System.out.println("Your unpacking directory or file cache does not exist!");
            return;
        }
        try (GZIPInputStream gzos = new GZIPInputStream(new FileInputStream(fileCache)); DataInputStream dataFile = new DataInputStream(gzos)) {
            int length = dataFile.readInt();
            for (int i = 0; i < length; i++) {
                int buffer = dataFile.readInt();
                String name = dataFile.readUTF();
                byte[] data = new byte[buffer];
                dataFile.readFully(data);
                saveToFile(name, data);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void saveToFile(String name, byte[] data) {
        try (FileOutputStream fos = new FileOutputStream(new File(unpackDir, name))) {
            fos.write(data);
            System.out.println("Saved: " + name);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        decompressContents();
    }
}