We don't walk through implementations of the standard patterns in this article. Given their number, this would be pretty lengthy and boring. Instead, we take a quick tour through the whole Java system, looking at features which are relevant for pattern implementation, and spotting pattern examples as we go. L AYER pattern. Looking at pattern-relevant language constructs, we mainly talk about idioms, not patterns themselves, i.e., ways to use the language in order to build patterns.
Interfaces are the most important language feature with respect to pattern implementation.
Classes are really simple in Java. The missing multiple inheritance is usually just an issue if we have to state-extend multiple classes in an existing class hierarchy, without changing inheritance relations. This is a very important aspect for patterns like S TATE , giving inner classes an outstanding role among language-specific pattern features. Reflection is the way to cross the magic boundary between names and life objects. Cloning is another feature for exemplar based patterns, where we construct objects out of existing ones.