When i load my file everything inside the class is null?

Newbie & Debugging Questions
#1

so i have a class SaveLevel and i save it fine but when i try to load it again everything inside the class is null?

SaveLevel class


public class SaveLevel  implements Serializable{
	
	static final long serialVersionUID = 99999999999999L;
	
	transient public ArrayList<Point> path = new ArrayList<Point>();
	transient public String imagePath;
	
	public SaveLevel(String imagePath){
		this.imagePath=imagePath;
	}
	
}

Loading Script


Level level = null;
		SaveLevel sLevel = null;
		
		ObjectInputStream ois;
		try {
			ois = new ObjectInputStream(getClass().getResourceAsStream(url));
			sLevel = (SaveLevel) ois.readObject();
			ois.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
		
		System.out.println(sLevel.imagePath);
		System.out.println(sLevel.path);
#2

[quote]transient is a Java keyword which marks a member variable not to be serialized when it is persisted to streams of bytes.
[/quote]
http://en.wikibooks.org/wiki/Java_Programming/Keywords/transient

#3

so i shouldnt use it? but im pretty sure when i dont use it i get a not serializable error

#4

So you threw in transient just to shut up the error without understanding what it’s for or why you got the error in the first place? Yeah … don’t program like that. Ever.

Is Point serializable?

#5

i imported point from java.awt.Point

#6

so yes it is serializable

btw it works without transient just that the array list is empty

#7

Are you certain the arraylist was populated when you saved it? I’m only asking because I’ve done boneheaded things like that. I was able to do the following and it worked:


package serialtest;

import java.awt.Point;
import java.io.Serializable;
import java.util.ArrayList;

public class SaveLevel implements Serializable {

	static final long serialVersionUID = 99999999999999L;
	   
	    public ArrayList<Point> path = new ArrayList<Point>();
	    public String imagePath;
	   
	   public SaveLevel(String imagePath){
	      this.imagePath=imagePath;
	   }
}



package serialtest;

import java.awt.Point;
import java.io.*;
import java.util.ArrayList;

public class SerialTest {


	public static void main(String[] args) {
		
		
	  // Create some Dummy information
      SaveLevel sLevel = new SaveLevel("Hi this is a test");
      
      
      ArrayList<Point> points = new ArrayList<Point>();
      points.add(new Point(1,1));
      points.add(new Point(2,2));
      points.add(new Point(3,3));
      
      sLevel.path = points;   
      
      String fileName ="c:\\level.dat";
   
      
      // Write the object to disk
      try {
         FileOutputStream fileOut = new FileOutputStream(fileName);
         ObjectOutputStream out =  new ObjectOutputStream(fileOut);
         out.writeObject(sLevel);
         out.close();
          fileOut.close();
      }catch(IOException i) {
          i.printStackTrace();
      }    
      
      // Make an empty saved level
      SaveLevel newLevel = new SaveLevel("");
      
      
      // Try to read the level back from the file
      ObjectInputStream ois;
      try {
    	  FileInputStream fileIn =  new FileInputStream(fileName);
    	  ois = new ObjectInputStream(fileIn);
      
         SaveLevel loadedLevel = (SaveLevel) ois.readObject();
         newLevel = loadedLevel;
         ois.close();
      } catch (FileNotFoundException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      } catch (ClassNotFoundException e) {
         e.printStackTrace();
      }
      
      
      // This should print out "Hi this is a test" and 3 points if it worked.
      System.out.println(newLevel.imagePath);
      System.out.println(newLevel.path);
	}

}

This worked (the restored arraylist has 3 elements). The main difference is that I didn’t use the getResource method to create the objectinputstream.

#8

The array used to store objects inside the arrayList is transient.
Reading the source code of the SE once as a java developer is just like the mecca for muslims ;D

#9

Interesting but wouldn’t my code then not work?

#10

Good question…
It … shouldn’t? ??? … confused ;D

EDIT: Okey… very quick edit (my Google-fu skillz are awezome…) Stackoverflow question bout that

I’m looking at the Serializable spec now… propably the ArrayList is treated special…