Concurrency (Threads)

Threads allow you to do tasks in parallel. In an unthreaded program, you code is executed

procedurally from start to finish. In a threaded program, you can have multiple

threads working concurrently.

Concurrency (Threads)

Concurrency is achieved through time-slicing. This is where the processor cycles through each active thread for an indeterminate period of time (the slice). This gives the illusion that there are multiple processes.

With multi-core processors, this may mean, true multi-threading is possible, but NOT guaranteed

Thread Pools

Thread Pools manage (and limit) the number of active threads. This tends to be more orderly and more efficient for scaled applications.

Synchronizing methods

When multiple threads have access to the same object, it makes sense to synchronize those methods which are prone to concurrency errors.

The bank account example.

Thread-safe collections

//http://download.oracle.com/javase/6/docs/api/java/util/concurrent/package-summary.html

Searching

Linear search O(n) --slowBinary search O(log2n) --fastRefresher on logs:

If 23 = 8 then log28 = 3

Hashed search O(1) –fastest

Search driver class

Sorting

SelectionSort O(n2) –-slowMergeSort O(n * log2n) –- fast

HeapSort O(n * log2n) –- fast

QuickSort O(n * log2n) –- fast