Tutorials : An Introduction to Multi-threading :

Thread Priorities

The example code defines three constants:

1. Thread.MIN_PRIORITY: This has a value of 1.
2. Thread.NORM_PRIORITY: This has a value of 5.
3. Thread.MAX_PRIORITY: This has a value of 10.

Thread States

Ready: A thread is in Ready state when it's ready for execution, but not actually being executed. A thread in this state qualifies for access to the CPU, in order to enter into the Running state.

Running: A thread is in Running state when it's being executed. This thread has access to the CPU.

Dead: A thread is in Dead state when the execution of the run method is completed. When a thread is dead, it can no longer be executed.

Waiting: In this state, the thread is waiting for an instruction. The instruction can be to release a monitor, sleeping, etc. A thread in this state qualifies to reach Ready state only after the instruction has been issued.

Synchronized Keyword

To use this keyword, place it in the signature of a method as shown in the code below. Placing a synchronized keyword in the signature of a method restricts the execution of An object's synchronized block of code to only one thread at a time. If a thread has already started executing your synchronized block of code for an object, no other thread can start to execute the block of code for that same object until the thread in action completes the synchronized method:

public synchronized void syncMethod() {
   if(! isAlreadyProcessed)
	{
     	isAlreadyProcess = true;
		//Do other activities
	}
}

Use Threads Wisely

Though designing a multi-threaded application is most always advisable, their injudicious use can result in memory or stack issues.

Related Resources

• The Java Tutorials: Lesson: Concurrency

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