Problem reading previously valid file
Hello,
Sorry for this dissertation but it is necessary in order to understand what is going on:
I have created a Bank system for a course (already graded so this is for my own knowledge). In this system I have an ArrayList of BankAccount types being written to a file via an ObjectOutputStream, each of these BankAccount objects contains some number of Transactions. When testing this program the GUI reads in the ArrayList and prints out the Transaction values so I can verify they are being stored. It worked perfectly. I submitted the program and it took the professor like 2 weeks to grade it (because he sucks at his job). In his evaluation of my program, which worked when I submitted it, he said that he got a NullPointerException when the Transactions are to be displayed. I tried running my program and, sure enough, the same file which worked before now caused NullPointerExceptions and I had not modified the project at all since submitting it.
I have no idea how this could be and was hoping someone could enlighten me as to why this might happen.
