Methods with reference type parameters in Java receive references to objects, not copies. When you pass an object to a method 'void process(Customer customer)', the method receives a reference to the original object. Changes to the object inside the method affect the original object. However, reassigning the parameter ('customer = new Customer();') only changes the local reference, not the caller's reference. Understanding reference parameter semantics is crucial for predicting method behavior and avoiding bugs.

Mastering reference parameters enables you to write methods that work with objects correctly. Understanding that objects are passed by reference affects how you design methods—methods can modify object state but not replace objects from the caller's perspective. In professional development, reference parameters appear everywhere: processing collections, modifying domain objects, configuring objects. For example, 'updateUser(user);' modifies the user object, while 'list.add(item);' modifies the list. Understanding this prevents confusion about method side effects.

By learning reference parameter semantics, you'll understand Java's parameter passing model deeply. Knowing when methods should modify parameters versus return new values is crucial for good design. This knowledge is fundamental to working with objects. Prerequisites include understanding references, objects, and basic method parameters in Java.