On: Ask HN: I have to analyze 100M lines of Java – where do I start?

[jebblue]

jvisialvm comes with the JDK, I'd start there with profiling:

http://visualvm.java.net/profiler.html

Edit: Adding, I'd set some judicial breakpoints in the hot spot areas identified through profiling along with some System.out.println's (or better dump to a flat file database, SQL can be used to work wonders for analysis even for flat file data).