Next Generation Wireless Applications: Creating Mobile Applications in a Web 2.0 and Mobile 2.0 World, 2nd Edition

11.8 JAVA 2 MICRO EDITION – ‘WIRELESS JAVA’

We have just looked at some Java fundamentals. We learnt that Java is both a programming language and a runtime environment, including APIs. Earlier in the book, we learnt about a very powerful technology for implementing scaleable backend systems called J2EE. Most of the goodness of J2EE was in its huge set of powerful software mechanisms to enable interfacing to myriad enterprise systems, such as databases and directories. All these powerful utilities in J2EE are implemented in Java and work using the underlying processes just described, such as using a JVM, Java APIs, class loading and so on.

Figure 11.22 shows that with a JVM available on a target machine, we should be able to run Java. This is highly attractive to developers as it means they can focus their efforts on mastering one language that will allow them to create applications for any type of environment, especially for mobile devices where there are huge numbers ready for running all those interesting mobile services we want to go on to develop. However, as the figure shows, our thoughtful developer is rather curious that this all seems a bit too easy. If, like our curious developer, we ponder for a moment on the implications of what is shown in Figure 11.22, we might start to realise some of the problems here, especially when taking into account the differences between the devices shown in the figure.

Figure 11.22 Will Java really run everywhere the same?

Two issues might ...