Flex for Java Developers

There are several articles online which discuss developing Flex from the Java developer's perspective.

As someone who has trained a lot of Java developers in Flex, I thought I'd share some of the recurring themes in their reactions to Flex as a platform. The vast majority of Java developers that receive Flex training end up convinced that, for them, it is a much easier and faster way to create client-side applications than Swing or AWT.

So what are some things to look out for?

Actionscript 3 looks a lot like Java, but it's not. Actionscript has a few characteristics that trip up first-time Java Flexers:

1. Syntax: It takes a while to re-train the fingers to type
   var myName:String = 'Fred';
   rather than
   String myName = 'Fred';
2. No overloaded methods, so you may have to pass in an object and inspect its properties if there may be variations in the number/type of parameters you want to pass in.
3. No private constructors, so if you need to create a Singleton, you're going to have to be a bit clever (or simply look at the ModelLocator in Cairngorm).
4. Only one superclass can be extended.
5. No abstract classes, but you can code around this by making a class whose constructor throws an error.

The data types in Actionscript are a bit looser than in Java. For example, a number which is a float or double in Java, is simply a Number in AS3. Also, AS3 has some constructs which you don't find in Java, such as the ArrayCollection.

The way in which source code is compiled is very similar to Java. The SWF file is analogous to a compiled Java .class file. A SWC is like a JAR and its classes can be used if the compiler knows where to find them.

Many Java developers are surprised at Flex's ability to easily communicate with many different back-end systems and formats: XML over HTTP, web services, server-side Java classes, .NET (via web services or Flash Remoting), etc.

Let me know if you come from a Java background and found something about Flex that you would like to pass on to others.