a) Garbage Collector : Non-deterministic memory management could be a problem

b) Lack of third party libraries: Most of the available libraries do not support Java. Java has huge class library built in but they are not game related

c) Not supported by game Console: Java is not supported by popular game consoles.

d) Smaller Community: Most game programmers use C++ , so if you are developing games on Java, you can expect least help from others as very few programmers can give you the solution for your query.