Does the software have a dll interface or some place you can 'hook in'?
What do you mean?
Java doesn't have DLL but JAR (it's the same).
do you implement your own triggers or does it come with predefined triggers/algorithms?
I have a trading algorithm I am working on but all my work is in c++
I Have written 100% of Java Code, so all triggers, check, condition etc are written by me.
I Use only "standard" library.