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Android Architecture ( Synchronization and Scheduling )

Java Classes

  • ReentrantLock
    • A reentrant mutual exclusion lock that extends the built-in-monitor lock capabilities
  • ReentrantReadWriteLock
    • Improves performance when resources are read much more often than written
  • Semaphore
    • A non-negative integer that controls the access of multiple threads to a limited number of shared resources
  • ConditionObject
    • Block thread(s) until some condition(s) becomes true
  • CountDownLatch
    • Allows one or more threads to wait until a set of operations being performed in other threads complete
Considerations
  • ReentrantLock have lower overhead than ReentrantReadWriteLock
  • ReentrantReadWriteLock may enable more concurrency on multi-core or multi-processor hardware
  • ConditionObject & Semaphore have higher overhead than ReentrantLock & ReentrantReadWriteLock
  • ConditionObject & Semaphore are more expressive & more flexible
  • ConditionObject can be used to lock a thread to keep other threads out of a critical section or keep in the critical section

ReentrantLock

Use mutual exclusion
Example: The bathroom in an airplane, only one person can use it at time

In Android implements the lock Interface and uses the Ganga four bridge pattern

Methods

  • lock()
  • lockInterruptibly()
    • acquires the lock unless thread is interrupted
  • unlock()

Readers-Witer Locks

  • Is a synchonization mechanism often used in context with many concurrent threads
  • Allow access to a shared resource
    • Where multiple threads have read-only access OR
    • one thread has write access
  • Human Example 
    • Formal Political debates: Many people listen the debate but only one person talk

RentrantReadWriteLock


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