Question: I find reading coding style guidelines to be the best way to get to know a language and its peculiarities. I've been trying to find a good document for Java, and get some questions answered immediately. 

Firstly, what is the convention for very long lines? Writing in both Java and C/C++ leads me to have a great deal of confusion on this point. 

Secondly, what is the guideline for creating custom exception classes? I typically end up throwing an existing exception rather than creating my own. Is custom exception creation typically enforced?

Answer: 
Take a look at the official [Code Conventions for the Java TM Programming Language](http://www.oracle.com/technetwork/java/codeconv-138413.html).
Possible duplicate question. You can find the answer here: <https://stackoverflow.com/questions/1334204/official-java-code-guidelines-conventions>

However, the documentation on Sun/Oracle's website is older than 12 years. Although the core language hasn't changed, technology changes rapidly, which means the way we work with that technology changes. 

I would suggest using what works best for you and your team. As long as there is some agreed-upon standard within your organization that is considered mainstream, you should be okay.