Removing Listener: "variable mouseListener might not have been initialized"

Upon initial compiling, I receive the error: "variable mouseListener might not have been initialized"
I choose the available option "initiatialize variable mouseListener"

After compiling, I receive the error message "cannot assign a value to final variable mouseListener"

Last evening while working on this I researched and came across a way to accomplish my goal. I am using what I see as a reference.

The following snippet demonstrates creating this reference to mouseListener:



At this time, after compile, I'm receiving an error message that using = null is not permitted (which appears to send me into a sort of circle, hence the apparent need for a reference.)

(The primary goal is to remove a mouselistener in order to simulate mouse freeze but first I need to figure this out. Thank you kindly for any nudge in the correct direction.)

If you need to reassign different objects to a variable then it cannot be final. By declaring your variable as final you are telling the compiler that once it has been assigned an object then you have no intention of ever changing your mind and you want the compiler to forbid it.

In your case here the final keyword behaviour is in opposition to your intended design so you'll want to remove it.

Tim Cooke wrote:If you need to reassign different objects to a variable then it cannot be final. By declaring your variable as final you are telling the compiler that once it has been assigned an object then you have no intention of ever changing your mind and you want the compiler to forbid it.

In your case here the final keyword behaviour is in opposition to your intended design so you'll want to remove it.

When I remove Final, I receive the error "local variables referenced from an inner class must be final or effectively final"

Ah well in that case your intended design cannot be brought into reality. Instead you could implement a "freezable mouse listener" or something similar, where the listener code checks whether it's in a freeze or not and responds accordingly.

Declaring and assigning the final variable at the same time will resolve your problems related to variable assignment. E.g:

On the implementation of the FreezableMouseListener, you got some solid advice in your other topic a few days ago that should put you in the right direction with it.

Tim Cooke wrote:On the implementation of the FreezableMouseListener, you got some solid advice in your other topic a few days ago that should put you in the right direction with it.

I greatly appreciate the assistance and while busy attempting to  implement this, new issues have cropped up and while in the same area of the project, the answers seem entirely different. Thanks again.

I have a sneaking suspicion that this code would be better implemented as a lambda these days.

MouseListener and MouseMotionListener are not Functional Interfaces, so you cannot use lambda's here.

@Mat
If you use (see lines 1 and 2 in your opening post)

then, for the compiler, mouseListener is a MouseListener. And so you cannot directly do:

because addMouseMotionListener requires a MouseMotionListener, and not a MouseListener.
A simple remedy would be what is called a CAST  (transforming for a moment from one type to another type)

But much easier is it to declare:

and then in the constructor:

And since a MouseAdapter is both a MouseListener and a MouseMotionListener, you can simply do:

This is what I did in the code in the previous topic, that Tim referred to in his post.

Thank you, working on this right now. Appreciate it.

Please avoid quoting the whole of the preceding post. That adds nothing and is liable to removal.