The built-in date/calendar functionality in Java is horrible compared to System.DateTime. There is a lot of info about this here: What's wrong with Java Date & Time API?What's wrong with Java Date & Time API?
Some of these can be gotchas for a C# developer:
- The Java Date class is mutable which can make returning and passing dates around dangerous.
- Most of the java.util.Date constructors are deprecated. Simply instantiating a date is pretty verbose.
- I have never gotten the java.util.Date class to interoperate well with web services. In most cases the dates on either side were wildly transformed into some other date & time.
Additionally, Java doesn't have all the same features that the GAC and strongly-named assemblies bring. Jar Hell is the term for what can go wrong when linking/referencing external libraries.
As far as packaging/deployment is concerned:
- it can be difficult to package up web applications in an EAR/WAR format that actually install and run in several different application servers (Glassfish, Websphere, etc).
- deploying your Java app as a Windows service takes a lot more effort than in C#. Most of the recommendations I got for this involved a non-free 3rd party library
- application configuration isn't nearly as easy as including an app.config file in your project. There is a java.util.Properties class, but it isn't as robust and finding the right spot to drop your .properties file can be confusing
