How to retrieve useful system information in java?

Question

Which system information are useful - especially when tracing an exception or other problems down - in a java application?

I am thinking about details about exceptions, java/os information, memory/object consumptions, io information, environment/enchodings etc.

Answer 1

For pure java applications:

System.getProperty("org.xml.sax.driver") 
System.getProperty("java.version")
System.getProperty("java.vm.version")
System.getProperty("os.name")
System.getProperty("os.version")
System.getProperty("os.arch")