Is there a way to monitor methods so that another method is executed elsewhere in the code?

Can someone help me and explain how best to observe a method. This means that when a certain method is executed, the entire system should be recalculated internally at another point, for example. The same for example when a file is uploaded, then certain calculations should be triggered in the background.

Observer is deprecated and PropertyChangeListener does not help me in my case i think.

Does anyone have an idea or pattern how to map this case in Java?

Thanks