Incorrect thread usage in SynchronizedItemStreamReaderTests

[spring-projects-issues]

Dimitrios Liapis opened BATCH-2767 and commented

While working on the PR for BATCH-2752 I found out that SynchronizedItemStreamReaderTests and SynchronizedItemStreamReaderBuilderTests have the following issue: 

The test threads are not properly started but rather their run method gets invoked

 I've addressed this issue and also performed some refactoring.

Few points about the approach followed:

• using an atomic integer to track access to the read method
• using a CountDownLatch to get all the threads ready
• using assertion within the read method (closely paired with the atomic integer above)

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Referenced from: pull request #666