The wonderful world of threads

1
The wonderful world of threads

• What is a thread, exactly? A piece of thin
  material used for holding together fabric? A
  message topic on a bulletin board? A discreet
  process fragment? All of these are true, but
  only one is interesting to us tonight.
• You all brought your needles, right?

2
Ok, maybe not.

• A java program consists of one or more threads.
  A thread is a single sequential flow of control
  within a program.
• Threads are like processes inside of the
  application, but they dont get their own memory.
  Each does have its own stack.
• Most applications have only one thread, the Main
  thread.

3
So why do we need more?

• I tell ya, in my day, we didnt have no fancy
  threads. We just worked twice as hard in one!
• You will need to use threads any time you want
  your program to perform two operations
  concurrently.
• Besides, it sounds really cool to say that your
  program is multithreaded.

4
Can I get an example, please?

• Timers
• Polling jobs (listeners)
• Background jobs

5
Using Thread

• The simplest option is to use methods declared in
  the Thread class, or to use high level thread
  APIs like the java.util.Timer().
• These APIs are very specific to certain tasks,
  however, and arent particularly customizable.
• So, you probably want to make your own.

6
So, how do I make one?

• In java, you just need to extend the class
  Thread.
• The code you want your thread to execute goes in
  the run() method. You start and stop your thread
  with start() and stop(), respectively.
• Your new thread will get spawned from another
  thread, probably the Main thread. This means
  that the Main thread will declare the new Thread
  object and call start() and maybe stop(), on it.

7
Code Example

• Why dont we look at an implementation of a
  timer.
• Why the heck couldnt I have gone over this
  before the project was due? Because Im mean.