Homework #5

1. (5 points) The HardwareData class abstracts of the idea of the get-and-set and swap hardware instructions. However, this class is not thread-safe because multiple threads may concurrently access its methods and thread safety requires that each method be performed atomically. Rewrite the HardwareData class using Java synchronization so that it is thread safe. See Thread1 and Thread2 classes which employ the get-and-set and swap hardware instructions, respectively.
   
   
2. (15 points) Consider only 3 thread types (A, B, and C) with the following constraints:
   
   
   • mutual exclusion among the A's,
   • mutual exclusion between the B's and C's,
   • mutual exclusion between the A's and C's, and
   • priority to the A's.
     
     
   Using only the Factory, Thread1, and SleepUtilities classes, complete the definition of the Java monitor Monitor class to solve this problem. Do not modify these classes at all. Complete only the data member section and provide defintions for the constructor and the 6 entry and exit methods.
   
   
3. (12 points) The Sleeping-Barber Problem: a barbershop consists of a waiting room and n chairs and a barber room with one barber chair. If there are no customers to be serviced, the barber goes to sleep. If a customer enters the barbershop and all chairs are occupied, then the customer leaves the shop. If the barber is busy but chairs are available, then the customer sits in one of the free chairs. If the barber is asleep, the customer wakes up the barber.

   Write a Java program using semaphores to coordinate the barber and the customers. Specificially, using only the Customer, Factory, and SleepUtilities classes, complete the definition of the BarberShop class. Do not modify these classes at all. Only complete the data member section and provide definitions for the constructor and the customerEnters(int id) method.

How to submit

1. Prepare your source code files as /home/<logname>/homeworks/hw5/HardwareData.java, /home/<logname>/homeworks/hw5/Monitor.java and /home/<logname>/homeworks/hw5/BarberShop.java, where <logname> is your login name, e.g., cps346-01.01. Only these source files will be electronically collected from this location in your UNIX account on the deadline.
   
   
2. Convert your source code files into a pretty-printed pdf file by executing the following command lines on our system from the directory in your UNIX account containing your source files HardwareData.java, Monitor.java, and BarberShop.java.

   a2ps HardwareData.java -o HardwareData.ps
   a2ps Monitor.java -o Monitor.ps
   a2ps BarberShop.java -o BarberShop.ps
   ps2pdf HardwareData.ps
   ps2pdf Monitor.ps
   ps2pdf BarberShop.ps
   

   or simply

   a2ps HardwareData.java
   a2ps Monitor.java
   a2ps BarberShop.java
   

   which will cause HardwareData.java, Monitor.java, and BarberShop.java to be printed to the printer in the AN 131 lab.
   
   
3. Submit a printouts of HardwareData.pdf, Monitor.pdf, and BarberShop.pdf in class at 3:00pm.