Architecting Modern Java EE Applications

Decorator

Another well-known design pattern is the decorator pattern. This pattern allows us to add behavior to an object without affecting other objects of that class. Quite often this behavior is composable with several subtypes.

A good example is food. Everybody has their own preferences in tastes and compositions. Let's take coffee as an example. We can drink just plain black coffee, with milk, with sugar, with both milk and sugar, or even with syrup, cream, or whatever will be popular in the future. And that's not taking into account the different ways of how to brew coffee.

The following shows a realization of the decorator pattern using plain Java.

We specify the following Coffee type which can be decorated using the sub-type CoffeeGarnish ...