Java Senior Engineer --- multi-thread concurrency

• Thread Pool (in Java 5)

Executorservice threadpool = executors. newfixedthreadpool (3); // create a fixed thread pool

Executorservice threadpool = executors. newcachedthreadpool (); // create a cache thread pool, dynamically change the number of threads, and destroy unused threads after a period of time

Executorservice threadpool = executors. newsinglethreadexecutor (); // create a single thread. When the thread dies, immediately start the backup thread.

• Lock condition for Synchronous thread Communication

Lock is similar to synchronized, but more object-oriented than synchronize

Use: lock = new reentranlock ();

Lock. Lock (); lock. Unlock ();

• Readwritelock RWL = new reentrantreadwritelock ();

Implementation of the cache system -------

Public class cachedemo {

Private Map <string, Object> cache = new hashmap <string, Object> ();

Private readwritelock RWL = new reentrantreadwritelock ();

Public object getdata (string key ){

RWL. readlock (). Lock (); // No locks can be applied between reads. If there is no value in the memory, read the database and write data to the cache.

Object value = NULL;

Try {

Value = cache. Get (key );

If (value = NULL ){

RWL. readlock (). Unlock (); // if no data exists, you must unlock the read and enable the write lock.

RWL. writelock (). Lock ();

Try {

If (value = NULL) {// multiple threads are routed to rml. writelock (). lock (), after a thread is successfully written, the following thread determines whether there is data in the cache when it comes to this step.

Value = "AAA ";

}

}

Finally {

RWL. writelock (). Lock ();

}

RWL. readlock (). Lock ();

}

 

}

 

Finally {

RWL. readlock (). Unlock ();

}

Return value;

}

}