Computer Science 225
Advanced Programming

Spring 2021, Siena College

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Agenda

• Announcements
  • Lab 8: Animation (in Canvas and GitHub)
    • due 24 hours before your lab session next week
    • if you have finished the required functionality (as many have) and decide to go back to add some bonus functionality, be sure to let me know so I notice it
  • Final Project
    • proposals now due
  • Exam 2 grading status
  • Problem Set 6 - see Canvas for links and intro video
• Thread safety
  • a data structure example of a race condition
  • intrinsic locking with synchronized methods
  • explicit locks to enforce mutual exclution in critical sections
• In-class exercise (3 points), create a document in your CSIS 225 shared Google drive folder.

  From the current topic notes:

  We have a list with one element:

    SimpleLinkedList<Integer> x = new SimpleLinkedList<Integer>();
    x.add(1);
  

  Then two threads each try to remove a value to make use of it in some way:

    if (!x.isEmpty()) {
      int val = x.get(0);
      x.remove(0);
      // do something 
    }
  

  What is the intended behavior here? What could go wrong?

• Java Packages
  • Java API packages and modules
  • using packages

Terminology

• thread safety
• granularity
• intrinsic lock
• mutual exclusion
• critical section
• explicit lock
• package
• module
• fully qualified name
• wildcard imports
• default package

Examples

• SynchronizedBallTosser: ball tossing again, but with thread safely using explicit locks.
• TwoTimers: a class conflict from wildcard imports
• ThreadGraphicsPackage: creating your own package, base classes to factor out some code common to graphics animations