Design patterns·Objects, messages and the principles
the method body is one line that calls the same method on a field, and that is the whole class's job for that method.
Delegation
Also calledforwarding, delegate to
Holding another object and forwarding work to it, exposing only what you choose to expose. It is what composition looks like at the method level, and it is the mechanism behind every wrapper pattern in the structural cluster. It costs boilerplate — one forwarding method per operation, which is why languages that generate delegation automatically make composition noticeably more attractive.