NullPointerException when trying to save file to hardrive Level7.

[Marcon2509]

I am attempting Level 7. Save and I am trying to use serialization to save an array which stores my list that is printed out. However my method saveData(ArrayList list) gets the nullPointer error as shown in the image above. I am using intelliJ

Below is my SaveData method (Note not sure why the insert code button isnt working)

public void saveData(ArrayList<Task> listToSave) {
      
  FileOutputStream fos = null;
       
 try {
            
fos = new FileOutputStream(dataFile);

        } catch (FileNotFoundException e) {
          
  
e.printStackTrace();

        } finally {

            if (fos != null) {

                ObjectOutputStream oos = null;
                try {

                    oos = new ObjectOutputStream(fos);

                    if (oos != null) {

                        oos.writeObject(listToSave);

                    }
                    assert oos != null;
                    oos.close();

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }


    }

[damithc]

Note not sure why the insert code button isnt working)

I updated your post to use the triple-back-tick notation for fenced code blocks.

See https://docs.github.com/en/github/writing-on-github/creating-and-highlighting-code-blocks

In think others need to know exactly which statement is causing the NPE i.e., which statement is at Storage.java:36

[Marcon2509]

The image above shows the nullPointerException is coming from fos = new FileOutputStream(dataFile);

[wakululuu]

Have you handled the case where dataFile doesn't exist?

[Marcon2509]

i think i do in the initFile method @wakululuu

[wakululuu]

Could you try printing the dataFile object and see what the output is?

[Marcon2509]

@wakululuu added the system.out.println(datafile) and in the picture shows i intialise it at the begining

[wakululuu]

Sorry for the unclear suggestion previously but maybe print it right before fos = new FileOutputStream(dataFile); instead. Could you also show the part of your code where you call saveData?

[zhiayang]

doesn't the error writing aborted; java.io.NotSerialisableException: ToDo suggest that your class ToDo does not implement the Serialisable interface

[Marcon2509]

@zhiayang ah yes my bad that was the problem thank you