| 33 |
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conservative in selecting only those APIs and implementations that are |
| 34 |
|
useful enough to encourage nearly all concurrent programmers to use |
| 35 |
|
routinely. JSR 166 also includes a few changes and additions in |
| 36 |
< |
packages outside of java.util.concurrent: java.lang, to address timing |
| 37 |
< |
and uncaught exceptions, and java.util to better integrate queues, and |
| 38 |
< |
to make Timers conform to new frameworks. The API covers: |
| 36 |
> |
packages outside of java.util.concurrent: java.lang, to address |
| 37 |
> |
uncaught exceptions, and java.util to better integrate queues. |
| 38 |
> |
The API covers: |
| 39 |
|
|
| 40 |
|
<ul> |
| 41 |
|
<li> Queues |
| 44 |
|
<li> Condition variables |
| 45 |
|
<li> Atomic variables |
| 46 |
|
<li> Timing |
| 47 |
< |
<li> Barriers |
| 47 |
> |
<li> Synchronizers |
| 48 |
|
<li> Concurrent Collections |
| 49 |
|
<li> Uncaught Exception Handlers |
| 50 |
|
</ul> |
| 77 |
|
java.util.LinkedList will be adapted to support Queue, and |
| 78 |
|
a new non-thread-safe java.util.HeapPriorityQueue will be added. |
| 79 |
|
|
| 80 |
< |
<p> |
| 81 |
< |
Four implementations in java.util.concurrent support the extended |
| 80 |
> |
<p> Five implementations in java.util.concurrent support the extended |
| 81 |
|
BlockingQueue interface, that defines blocking versions of put and |
| 82 |
< |
take: LinkedBlockingQueue, ArrayBlockingQueue, SynchronousQueue, and |
| 83 |
< |
PriorityBlockingQueue. Additionally, java.util.concurrent.LinkedQueue |
| 84 |
< |
supplies an efficient thread-safe non-blocking queue. |
| 85 |
< |
<p> |
| 86 |
< |
Since the target release is JDK1.5, and generics are slated to be in |
| 87 |
< |
1.5, Queues should be parametrized on element type. (Also some others |
| 88 |
< |
below.) We are ignoring this for now. |
| 82 |
> |
take: LinkedBlockingQueue, ArrayBlockingQueue, SynchronousQueue, |
| 83 |
> |
PriorityBlockingQueue, and DelayQueue. Additionally, |
| 84 |
> |
java.util.concurrent.LinkedQueue supplies an efficient thread-safe |
| 85 |
> |
non-blocking queue. |
| 86 |
> |
|
| 87 |
> |
<p> Since the target release is JDK1.5, and generics are slated to be |
| 88 |
> |
in 1.5, Queues are parametrized on element type. (Also some others |
| 89 |
> |
below.) |
| 90 |
|
|
| 91 |
|
|
| 92 |
|
<h2>Executors</h2> |
| 95 |
|
thread-like subsystems, including thread pools, asynch-IO, and |
| 96 |
|
lightweight task frameworks. Executors also standardize ways of |
| 97 |
|
calling threads that compute functions returning results, via |
| 98 |
< |
Futures. This is supported in part by defining java.lang.Callable, the |
| 98 |
> |
Futures. This is supported in part by defining interface Callable, the |
| 99 |
|
argument/result analog of Runnable. |
| 100 |
|
|
| 101 |
|
<p> While the Executor framework is intended to be extensible the most |
| 105 |
|
majority of usages, even sophisticated ones, yet also includes methods |
| 106 |
|
and functionality that simplify routine usage. |
| 107 |
|
|
| 108 |
– |
<p> |
| 109 |
– |
A few methods will also be added to the java.util.Timer to support |
| 110 |
– |
Futures, and address other requests for enhancement. |
| 111 |
– |
|
| 108 |
|
<h2>Locks</h2> |
| 109 |
|
|
| 110 |
|
The Lock interface supports locking disciplines that differ in |
| 162 |
|
Java has always supported sub-millisecond versions of several native |
| 163 |
|
time-out-based methods (such as Object.wait), but not methods to |
| 164 |
|
actually perform timing in finer-grained units. We address this by |
| 165 |
< |
introducing java.lang.Clock, which provides multiple granularities for |
| 165 |
> |
introducing class Clock, which provides multiple granularities for |
| 166 |
|
both accessing time and performing time-out based operations. |
| 167 |
|
|
| 168 |
|
|
| 169 |
< |
<h2>Barriers</h2> |
| 169 |
> |
<h2>Synchronizers</h2> |
| 170 |
|
|
| 171 |
< |
Barriers (multiway synchronization points) are very common in some |
| 172 |
< |
styles of parallel programming, yet tricky to get right. The two most |
| 173 |
< |
useful flavors (CyclicBarriers and Exchangers) don't have much of an |
| 174 |
< |
interface in common, and only have one standard implementation each, |
| 175 |
< |
so these are simply defined as public classes rather than interfaces |
| 176 |
< |
and implementations. |
| 171 |
> |
Five classes aid common special-purpose synchronization idioms. |
| 172 |
> |
Semaphores and FifoSemaphores are classic concurrency tools. Latches |
| 173 |
> |
are very simple yet very common objects useful for blocking until a |
| 174 |
> |
single signal, event, or condition holds. CyclicBarriers are |
| 175 |
> |
resettable multiway synchronization points very common in some styles |
| 176 |
> |
of parallel programming. Exchangers allow two threads to exchange |
| 177 |
> |
objects at a rendezvous point. |
| 178 |
|
|
| 179 |
|
|
| 180 |
|
<h2>Concurrent Collections</h2> |
| 181 |
|
|
| 182 |
< |
There are no new interfaces, but JSR 166 will supply a few Collection |
| 183 |
< |
implementations designed for use in multithreaded contexts: |
| 184 |
< |
ConcurrentHashTable, CopyOnWriteArrayList, and CopyOnWriteArraySet. |
| 182 |
> |
JSR 166 will supply a few Collection implementations designed for use |
| 183 |
> |
in multithreaded contexts: ConcurrentHashTable, CopyOnWriteArrayList, |
| 184 |
> |
and CopyOnWriteArraySet. |
| 185 |
|
|
| 186 |
|
<h2>Uncaught Exception Handlers</h2> |
| 187 |
|
|
| 192 |
|
of features in JSR 166 make ThreadGroups even less likely to |
| 193 |
|
be used in most programs. Perhaps they will eventually be deprecated.) |
| 194 |
|
<p> |
| 195 |
< |
Additionally, Threads and ThreadLocals will now support a means to |
| 196 |
< |
clear and remove ThreadLocals, which is needed in some thread-pool and |
| 195 |
> |
Additionally, ThreadLocals will now support a means to |
| 196 |
> |
remove a ThreadLocals, which is needed in some thread-pool and |
| 197 |
|
worker-thread designs. |
| 198 |
|
|
| 199 |
|
<hr> |
