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Synchronizing Threads
So far, this lesson has contained examples with
independent, asynchronous threads. That is, each thread contained all of
the data and methods required for its execution and didn't require any
outside resources or methods. In addition, the threads in those examples
ran at their own pace without concern over the state or activities of any
other concurrently running threads.
However, there are many interesting situations where separate,
concurrently running threads do share data and must consider the state and
activities of other threads. One such set of programming situations are
known as producer/consumer scenarios where the producer generates a stream
of data which then is consumed by a consumer.
For example, imagine a Java application where one thread (the producer)
writes data to a file while a second thread (the consumer) reads data from
the same file. Or, as you type characters on the keyboard, the producer
thread places key events in an event queue and the consumer thread reads
the events from the same queue. Both of these examples use concurrent
threads that share a common resource: the first shares a file, the second
shares an event queue. Because the threads share a common resource, they
must be synchronized in some way.
Here is an example code using synchronization
method
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