Suggested small changes to Java code for slightly more standard style, encapsulation and in some cases performance

Sorry if this is too abrupt or not a welcome set of changes, but thought I'd see if I could contribute a little. I'm a Java developer and just getting seriously into Spark. So I thought I'd suggest a number of small changes to the couple Java parts of the code to make it a little tighter, more standard and even a bit faster.

Feel free to take all, some or none of this. Happy to explain any of it.