Code Smell – Bad Smell in Code : Understanding Lazy Class

The Java runtime has built-in lazy instantiation for classes. Classes load into memory only when they’re first referenced. (They also may be loaded from a Web server via HTTP first.)

Lazy class loading is an important feature of the Java runtime environment as it can reduce memory usage under certain circumstances. For example, if a part of a program never is executed during a session, classes referenced only in that part of the program never will be loaded.

Lazy object creation is tightly coupled to lazy class loading. The first time you use the new keyword on a class type that previously hasn’t been loaded, the Java runtime will load it for you. Lazy object creation can reduce memory usage to a much greater extent than lazy class loading.

One occurrence of LAZY-INITIALIZATION isn’t a serious problem, of course. However, there are normally many instances of little setup idioms like this in applications. Hence, the global setup strategy (if there is one) is scattered across the application, with little modularity and often significant duplication.

If we are diligent about building well-formed and robust systems, we should never let little, convenient idioms lead to modularity breakdown. The startup process of object construction and wiring is no exception. We should modularize this process separately from the normal runtime logic and we should make sure that we have a global, consistent strategy for resolving our major dependencies.