Overview:

Goals:

• Understand more about drawing on a Swing component (a JPanel)
• Understand how to arrange callbacks via Runnable
• Understand how to obtain and use double locks

Before starting:

• Read over this entire document before you start.
• Look over the documentation , but be aware that you don't implement all classes for this part.
• Run the sample solution for this lab.
• Have fun with the sample solution for the next lab . Try to spot the deadlock.
• If you need help, please ask.

• Files you are given:
  • Lab.java
  • Startup.java (tests your stuff)
  • LockInvokable.java
  • Scribbler.java
• Files you need to complete:
  • Room.java
  • RectViz.java
  • LockPub.java
  • DoubleLock.java

Suggested implementation plan:

• The Startup class has test code for this part. You can write more test code and are encouraged to do so.
• Implement Room. Look for the spots in the code where you must provide the implementation. Note: Think hard about what object the LockPub instances (4 of them per room) are trying to guard. It's not the north, south, east, west objects! Once this class emits its PCS signals, the test code in Startup will report it as such.
• Implement LockPub. The only method you have to implement is lockInvoke. That method must go through the process of requesting the lock (on o, not on itself), acquiring the lock, running the Runnable, and releasing the lock. See the JavaDoc for the signals that need to be emitted along the way. Once it emits its PCS signals, the testing code will show when locks are requested, granted, and become available again.
• Implement DoubleLock. Here again, the only method you implement is lockInvoke. Get a lock on o1, using its lockInvoke method, which should get a lock on o2 similarly, and then with both locks in hand, run the Runnable Testing code should now work on double locks. Note that the locks of a double lock are obtained in a random order; you should see this in your output.
• Implement RectViz and let the testing code show you how it works.

What to turn in:

1. Complete a code cover sheet.
2. Provide a printout of all class files you have modified.