Java SaveFile won't work I'm novice @Java Programming. I have been working for SaveFile, for my game. Load and Save data. I got 2 following errors:   java.io.EOFException at java.io.ObjectInputStream$BlockDataInputStream.peekByte(Unknown Source) at java.io.ObjectInputStream.readObject0(Unknown Source) at java.io.ObjectInputStream.readObject(Unknown Source) at Clicker.LoadFile.&lt;init&gt;(LoadFile.java:17) at Clicker.mainClass.main(mainClass.java:21)   java.lang.NullPointerException     at Clicker.SaveFile.&lt;init&gt;(SaveFile.java:17)     at Clicker.mainClass$1.run(mainClass.java:26)     at java.lang.Thread.run(Unknown Source)   I have got MainClass, where i put in SaveClass and LoadClass :  package Clicker;   import javax.swing.JFrame;  public class mainClass {   public static void main(String[] args) {       ClickerGame game = new ClickerGame();          JFrame frame = new JFrame("CarCollectionarV1");         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);          game.addComponentToPane(frame.getContentPane());          frame.pack();         frame.setVisible(true);         frame.setResizable(true);         frame.setSize(1000, 700);          LoadFile load = new LoadFile();   Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {          public void run() {         SaveFile save = new SaveFile();         }     }));  }   Full "SaveClass" code:    package Clicker;  import java.io.*;  public class SaveFile{      ClickerGame CG = new ClickerGame();{  try{     File SaveFile = new File("SaveFile.sav");     if(!SaveFile.exists()) {         SaveFile.createNewFile();     }      FileOutputStream saveFileSub = new FileOutputStream(SaveFile);     ObjectOutputStream save = new ObjectOutputStream(saveFileSub);      save.writeObject(CG.CarMain.Money);     save.writeObject(CG.CarMain.MoneyClicks);     save.writeObject(CG.CarMain.Boxes);     save.writeObject(CG.CarMain.BoxesClicks);     save.writeObject(CG.CarMain.PlayerLevel);     save.writeObject(CG.CarMain.BoxLevel);  save.close();     }     catch(Exception exc){     exc.printStackTrace();     }     } }   And Full "LoadClass" code:  package Clicker;  import java.io.*;  public class LoadFile {      ClickerGame CG =new ClickerGame();{          try{             File SaveFile = new File("SaveFile.sav");             if(!SaveFile.exists()) {                 SaveFile.createNewFile();             }              FileInputStream SaveFileSub = new FileInputStream(SaveFile);             ObjectInputStream load = new ObjectInputStream(SaveFileSub);              CG.CarMain.Money = (int) load.readObject();             CG.CarMain.MoneyClicks = (int) load.readObject();             CG.CarMain.Boxes = (int) load.readObject();             CG.CarMain.BoxesClicks = (int) load.readObject();             CG.CarMain.PlayerLevel = (int) load.readObject();             CG.CarMain.BoxLevel = (int) load.readObject();              load.close();             }             catch(Exception exc){             exc.printStackTrace();             }             }
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