You can expect to see questions related to the main() method on the certification exam. Make sure that you remember that it has the public and static modifiers and the void return type. Also, remember that its argument is of the String[] type.
You may also be asked a question on how command line arguments are accessed. Remember that args[0] references the first argument that is passed to the program. This is different from C and C++ programs where args[1] references the first command line argument.