Deferred Binding

Deferred Binding is one of the key features that lets GWT produce well-optimized JavaScript code. As you saw earlier, the GWT compiler doesn’t support Java Reflection or dynamic class loading (also referred to as dynamic binding). This is because the JavaScript environment in which GWT applications run in doesn’t support it. Because dynamic binding is unavailable to GWT, GWT instead uses something called deferred binding. Deferred Binding is similar to dynamic class loading. While dynamic class loading occurs at runtime, Deferred Binding occurs at compile-time.
When the GWT Compiler compiles your client-side code, it determines all of the different “browser idiosyncrasies” it must support, and generates a separate, highly optimized version of the application for every specific configuration. So at the end of the day the compiler will generate a different version of your application for each different supported browser. But there is more to Deferred Binding than just multi-browser detection and support. Deferred Binding is a fully generic mechanism for handling context sensitive features.
A good example of where Deferred Binding is useful is Internationalization. The GWT Compiler uses Deferred Binding to generate completely separate versions of your application for each language. So if GWT supports 4 browsers, and you write your application in 4 languages, GWT will generate a 16 different permutations of your application at compile-time. During bootstrapping, at runtime, GWT picks the appropriate version of your application to show the user.