Passing dynamic variables between classes

I wonder if its possible to pass dynamic variables between classes in java.

For example: Pass the variable a=(some input value that can change)
from one class to another.

You may need to study on the distinction between classes and objects. Since passing information between objects is usually pretty easy and often simply a matter of calling a setter method or passing a parameter into a constructor, you may wish to greatly clarify your question since we have no idea what your current problem is.

Much luck!