Game2048 | Some little self-made computer games | Game Engine library

Firstly, a NullPointerException generally occurs when you are trying to access something that hasn't been initialized yet. In your case, this is the .value() function.

In your second code block you may realize there is one major difference in the code you're using: this would be the "== null" part of your code as opposed to ".value() == MAX_PIECE".

Now, why would one of these throw an error while the other one does not?

This is because when you are checking if something is "null" you are seeing whether it exists or not. If it doesn't, then your program will return true, if it does exist, then your program will return false.

On the other hand, when you call .value() on an object you are already assuming the object exists. This means that, if the object has not been initialized for example, your program will attempt to dereference the pointer stored in your variable but will quickly realize that the pointer is not actually pointing to anything.

To fix an error such as this you simply need to make sure that what you're trying to access exists.

An example: lets say that we have Person x.