THREAD
Subject
Session
Tahun
Versi
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:
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T0934 / Multimedia Programming Foundation
3
2009
1/0
Learning Outcomes
In the end of this session, students must
be able to:
– Recognize Threads
– Understand the concept of
multithreading
– Use Threads and Multithreads in Java
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Course Outlines
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Thread
Why Multithreading?
Create and Start a Thread
Sleeping Thread
Runnable vs. Thread Class
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Thread
• A path of code execution through a program,
and each thread has its own local variables,
program counter, and lifetime
• Modern OS is able to do all in the same time
– read the slides
– opening the web browser
– copy files to USB flash-disk
All in the same time
• So, running multiple thread
means the programs are
running at the same time
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Thread
• Example:
Java code execution starts with the main()
method and proceed in a path until the
statements are completed. This is one thread.
Another thread is actually run by Java Virtual
Machine: the garbage collector thread. It cleans
up discarded objects and reclaim their memory.
Therefore, even a simple Java Program “Hello
World” actually use multithreaded environment.
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Multithread Animation
In Winamp, we could see
process of AVS, Music,
Equalizer, and Read
Events have their own
threads to run
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Why Multithreading
• If only one thread was available, a program can
only do one thing a time
• It’s not fun if a word processor program cannot
be used to open a second document while the
first was printed
• Allows user to do more than one action at one
time
• User doesn’t have to wait for the first process to
finish to start another
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Why Multithreading
• Running more than one thread also carry new
resources
• Many threads run at one time cost more memory
resources than one thread at a time
• Doesn’t limit how many thread that program can
make, but the costs of memory and processor
resources should be considered
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Create Thread
• Two ways to use threads in Java:
– 1. Extending the java.lang.Thread class
– 2. Implementing java.lang.Runnable interface
• Both ways has its own uniqueness
• The steps to spawn a new thread are:
– 1. Extends Thread class or implement Runnable interface
– 2. Override the run() method
– 3. Invoke the start() method
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Create Thread
A simple program to use a single thread.
In this program, the thread is running the run() method when start() is
invoked.
The result is printing the “Usage of thread” on the monitor.
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Create Thread
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Create Thread
• A simple program to use multi threads.
• The result may be like this.
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Sleeping Thread
• We could make a delay with Thread.sleep().
• Example in use: clock application.
• Example: delay 5 second (5000 ms)
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Runnable vs. Thread Class
• Java can’t extends 2 classes at once (eq.
extends from JFrame and Thread is
impossible)
• Use Runnable interface to replace Thread class
• Other than extending (in class)  implementing
(in interface)
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SampleTimer
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SampleTimer
• A simple timer to demonstrate derived
class from JFrame and implementing
Runnable.
• Full code is downloadable in Additional
Material (SimpleTimer.java)
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References
• Introduction to Java Programming. 7ed. Liang. 2009. Chapter 15.
• Java Thread Programming. 1ed. Hyde, Paul. 1999.
• Multi-Threading in Java. Tod Cunningham. 1998. http://java.syscon.com/node/35929
• Thread. Wikipedia. 2009.
http://en.wikipedia.org/wiki/Thread_(computer_science)
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