If they don't use them to sue people, what would be the point of having them.
The nuclear weapons analogy is very appropriate: You're not supposed to have to use them. If you actually end up litigating a patent, something has gone terribly wrong.
The problem is this: If you have a valid patent and you want to use it for exclusion like patents are intended (like pharmaceutical companies do), you don't end up in court, because your competitors know you have a valid patent and don't bother infringing it, or stop when you tell them to.
But that isn't what happens in the tech industry. Instead, everyone has a huge pile of overly broad and obvious patents which everyone else is infringing (and only because none of them should ever have been issued), and the cost of litigating that many patents is almost always prohibitive. The consequence is that no one can use them for exclusion, because as soon as you file a lawsuit you get one back and it's mutually assured destruction. At the same time, you still have to have a huge patent arsenal in order to deter all the other companies from going to you for a shake down using a huge pile of questionable patents that would almost always cost more to litigate and invalidate than license. In this case the problem was that Oracle was vastly overvaluing the patents -- they were claiming $6B in damages at the start of all this. Now it looks like if they win it's going to end up being more like something less than $50M. Which is almost certainly less than the amount Oracle is having to spend in legal fees.
The sole purpose of buying sun seems to be to attack google with their IP... for what purpose I don't know.
I don't know if that's really it. I think part of it is that there are a very large number of old, conservative, high-spending Oracle customers who use Sun hardware, and if Sun dies then those customers are going to be looking for a new vendor, and in the process they could end up being sold an Oracle competitor's database. So Oracle staged a Sun bailout. They just happened to end up with Java in the process.
The thing is, Java means something different to Oracle than it ever did to Sun. The original point of Java was to stop people from writing apps in Visual Basic or against the Win32 API which then wouldn't run on Solaris and SPARC -- Java was "write once, run anywhere" so you could write your app for whatever you have now and then Sun could come in at some point and pitch some hardware to you and it would still run your software.
Oracle is instead looking at it as a licensing opportunity. Lots of people are using Java, Oracle wants money. The problem is that their patents are crap and claiming copyright on an API is ridiculous. It's like claiming a copyright on the bolt pattern in a piece of industrial equipment so that no competitors can make replacement parts. It's purely functional, and copyright only covers expression, not function. Functionality is the domain of patents.