In the middle of a java code (class A), if I need to invoke another java class (class B) , which has its own logics there and some database process taking lot of time. It will hold my java class A execution because it is doing it sequencially in class A. How do I let that calling class B happen async so that class A can continue ? The pre-condition is -- class A does not depend on the result of invoking class B. How can that be implemented ?