Reading Minecraft-like binary files

I decompiled the first Minecraft version (rd-132211) using jd-gui and recompiled it. After recompiling, running Minecraft had no problem except screen size problem and I can make sure the source code has no problem.

Now, I looked at com.mojang.rubydung.level Level.java file. But I can’t understand lot.

Here is the code I understood and used in my code:

package com.kg.jopenattack.level;  import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.util.zip.GZIPInputStream; import java.util.zip.GZIPOutputStream;  public class Level {     private byte[] bytes = new byte[1];     public void load() throws FileNotFoundException, IOException {         DataInputStream dis = new DataInputStream(new GZIPInputStream(new FileInputStream(new File("level.lvl"))));         dis.readFully(bytes);         dis.close();     }     public void save() throws FileNotFoundException, IOException {         DataOutputStream dos = new DataOutputStream(new GZIPOutputStream(new FileOutputStream(new File("level.lvl"))));         dos.write(bytes);         dos.close();     } } 

But this code reads nothing.

To decompile Minecraft rd-132211, enable historical option in Minecraft launcher settings and create rd-132211 installation.