I saw a proposal this morning for Java closures (or some form thereof). For me, closures and list comprehensions are the two things that I could really use from the functional world. As it stands, I use functionalj when I want functional goodness in Java – it’s not perfect, but it much better than constantly declaring anonymous classes for callbacks.
I wish I could program in Python (or some such language) all the time, but the bottom line is that Java has a lot of advantages when one is building a shipping product. So, I plug along with it and wait for the crossover of language concepts from other languages.