Need help with this JAVA threading problem:

Write a class called TellerMachine that simulates an ATM. It should contain two methods deposit() and withdraw(). It also contains a private variable called accountBalance. The deposit() method allows a thread to deposit $500, and update the account balance. The withdraw() method allows a thread to remove $120, and update the account balance.

Write a main method that creates two threads. One of the threads (called Deposit Thread) should execute the deposit() method. The other thread (called Withdraw Thread) should execute the withdraw() method.

* You need to make sure that there is no race occurs between the deposit and withdraw threads.