How to share the same behaviour in different Classes?

I have a class called Process, which is extended by some different process types called ProcessA, ProcessB, …

class Process{}  class ProcessA extends Process{} class ProcessB extends Process{} //... class ProcessN extends Process{} 

There is also another class related to the data of A, but not the Process. I call it TempA

Now, ProcessA has a method called calculate(), TempA needs to be calculated in the same way as ProcessA as well. As ProcessA extends Process (and Java doesn’t allow multiple inheritance), I can’t make an abstract class like AbstractA and put calculate() method to make these two classes (ProcessA and TempA) have same calculation method.

So how do I make these two classes have the same calculation behaviour/method without copy/paste-duplication of methods?