When should I use Java.* APIs vs System.* ones?
There is some overlap between the Java.* classes and the System.* classes. With MonoDroid we exposed the Java.* namespaces to the .NET world to allow developers to call into any of the native Java APIs. In general, while building MonoDroid applications you should use the System.* classes over the Java.* classes for most of your code. The reason is because using the Java.* classes will actually create two instances of the object: one in the C# world that is the proxy to the real Java class, and one in the Dalvik side that implements the actual functionality. Every time that you invoke a method or a property in one of the Java.* classes, the code will transition from the Mono VM into the Dalvik VM and back. Most of the services exposed by the Java.* classes are available directly from the Mono world in the System.* namespaces and will not incur in this performance penalty. The exception to this rule is when you need to call a specific method in Android.* or Java.* that requires an instan
