Wrapper

An object that encapsulates and delegates to another object to alter its interface or behavior in some way.

Java won't let you change a caller's variable. However it will let you change the fields inside a caller's object passed to you as a parameter. To get around the limitation that you can't change the caller's variables, (or return multiple values), you create a dummy class. You can then have the caller pass you an object of that dummy class and you fiddle its fields. Alternatively you create such an object, fill in its fields and return it to the caller. That dummy class is called a wrapper.