I am doing my final year of undergraduation and I need a java simulator that simulates a parking lot.
Can anybody provide me with a simulator or suggest a open source simulator?
I have no backgroung in building simulators. Is it easy? If I had to build a simulator on my own, how long will it take?

You could at least try to get started before you ask for help. Work through it a little. What are the characteristics you're trying to model?

Consider a supermarket - in that situation you have some number of lines (queues) and a source of customers. Each customer takes some random number of seconds to process. Customers are generated at a rate of r customers per minute, and immediately join the shortest queue when generated. Set that up, and you can start varying parameters - the range in which time to process varies, the rate at which customers are generated, the number of queues. You can see whether it makes a difference if customers know the total time of a queue or if they can only see the length. You can make some of the queues slower, etc. All of this is pretty simple, once you set up the basic model.

Okay, so now consider your parking lot. How do you model that? How is the parking lot set up, and how does that affect things? What questions are you trying to ask with this model?

If you're in your last year of undergrad, you've done algorithms and data structures, right? What data structures might model a parking lot? (as opposed to the grocery store, for example)