Introduction
Threads Overview
  Demo 1   Demo 2
Stopping Threads
Multi-Processing
Thread Tasks
Animations
  Demo 3   Demo 4  
  Demo 5
Non-interacting
  Demo 6
Task Splitting
  Demo 7
Exclusivity
  Demo 8
Communicating
  Demo 9
Priority/Scheduling
More Thread
Exercises

    Supplements
Java2D Animation
  Demo 1 
Processor View
More Concurrency
Cloning
  Demo 2  Demo 3 

An operating system executes multiple processes in a manner similar to that for multi-threading, except that each process stack refers to a different program in memory rather than code within a single program. The Java Virtual Machine (JVM), of course, controls the threading within the Java programs, just as the machine OS controls multiple processes.

In some JVM designs, threads can be assigned to native kernel processes in the OS. Furthermore, for operating systems such as Solaris and Windows NT that can control multiple processors, the threads can actually run on different processors and thus provide true parallel processing performance.

Whether its for multithreading or multiprocessing, the two basic designs for this context switching, i.e. the shifting of threads/processes in and out of a processor, include

• preemptive or time-slicing - give each thread a fixed amount of time.
  
  
• non-preemptive or cooperative - a thread decides itself when to surrender control

Generally, the preemptive approach is the most flexible and robust. A misbehaving thread cannot hog all the resources or hang the processor. Unfortunately, the context switching is not specified for Java and so different JVM implementations do it differently. Thus you should design your multi-threaded code for either possibility if you want it to be suitable for broad distribution. This means adding yield()or sleep() calls to release control at suitable points in the thread code.

Latest update: Nov. 8, 2004

              Tech
Timers
  Demo 1
Hist. Adapt Range
  Demo 2
Sorting in Java
  Demo 3
Histogram Median
  Demo 4
Refactoring
  Demo 5
Error Bars
  Demo 6
Exercises

           Physics
Least Squares Fit
  Demo 1
Fit to Polynomial
  Demo 2
Fit Hist Errors
  Demo 3
Discretization
  Demo 4
Timing
  Demo 5
Exercises