Java throws NullPointerException - No stack trace

My java applcation is throwing a NullPointerException on some data. The applications is multithreaded application that takes data as input, processes it and sends it. On some of the data I get a NullPointerException , but no stack trace. After investigating them I did not see a difference between the data that causes NullPointerException and the data that doesn't. The only difference I get is that when the NullPointerException occurs the application has a high load.
2 answers

I do not know if you used any IDE, but in eclipse you can switch to the debug mode, and change between the different threads. In each thread you can see the stack trace.

Because the application is multithreaded and the error is occuring at high load-times, I realized that the application is not thread safe and that is probably the cause. So I looked into my classes and entities and realized that one class is not thread-safe because it has two attributes that were not accessed and edited in a thread safe way. The solution in java was to use Atomic classes for example AtomicInteger and to change the value using methods of this class. This way we make the class thread safe and NullPointerException is solved.