How do a write this in Java?

Use each of the concurrency techniques:

semaphores

message passing

To solve the following concurrency problem:

A parking lot with a capacity of N cars is on an island. A ferry with a capacity of M cars shuttles cars between the mainland and the island. The ferry may cross whenever there are no cars waiting to get on the ferry $($even if it is not full$)$ provided that there are cars waiting on the other side. The ferry may also cross whenever it is full or $($in the case of crossing to the island$)$ when the number of cars in the ferry would fill the parking lot.

You are to avoid deadlock and starvation. You may assume that the system contains more than N cars and that N is greater than M $.$ Your program must be demonstrably correct. I will not read code for the purposes of checking correctness. Your description of the algorithm should make its correctness clear and demonstrate the techniques of semaphores and message passing.