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Sat Sep 27 12:21:56 2003 UTC (18 years ago) by dl
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Noted that this is an update of PR spec

2     <html>
3     <head>
4 dl 1.12 <title>JSR 166 Introduction.</title>
5 tim 1.1 </head>
7     <body bgcolor="#ffffee" vlink="#0000aa" link="#cc0000">
8 dl 1.12 <h1>JSR 166 Introduction.</h1>
9 tim 1.1
10     by <a href="http://gee.cs.oswego.edu/dl">Doug Lea</a>
11     <p>
13 dl 1.14 This is an updated version of the specification submitted for JCP Public
14     Review. To check for further updates, access a preliminary prototype
15     release of main functionality, or join a mailing list discussing
16     JSR-166, go to: <A
17 dl 1.9 HREF="http://altair.cs.oswego.edu/mailman/listinfo/concurrency-interest">
18 dl 1.14 http://altair.cs.oswego.edu/mailman/listinfo/concurrency-interest</A>.
19 dl 1.7
20 dl 1.14 <p><em>Note: The javadocs here includes some existing java.util
21     Collection interfaces and classes that are not part of the JSR-166
22     spec, but are included because JSR-166 methods implement or inherit
23     from their specifications.</em>
24 dl 1.9
25     <p> JSR-166 introduces package <tt>java.util.concurrent</tt>
26     containing utility classes commonly useful in concurrent
27     programming. Like package <tt>java.util</tt>, it includes a few small
28     standardized extensible frameworks, as well as some classes that
29     provide useful functionality and are otherwise tedious or difficult to
30     implement.
32     <p>JSR-166 focusses on breadth, providing critical functionality
33     useful across a wide range of concurrent programming styles and
34     applications, ranging from low-level atomic operations, to
35     customizable locks and synchronization aids, to various concurrent
36     data structures, to high-level execution agents including thread
37     pools. This diversity reflects the range of contexts in which
38     developers of concurrent programs have been found to require or desire
39     support not previously available in J2SE, which also keeping the
40 dl 1.14 resulting package small; providing only functionality that it makes
41     sense to standardize.
42 dl 1.9
43     <p>Descriptions and brief motivations for the main components may be
44     found in the associated package documentation. JSR-166 also includes
45     a few changes and additions in packages outside of
46     java.util.concurrent. Here are brief descriptions.
47 tim 1.1
48     <h2>Queues</h2>
50 dl 1.3 A basic (nonblocking) {@link java.util.Queue} interface extending
51 dl 1.9 {@link java.util.Collection} is introduced into
52     <tt>java.util</tt>. Existing class {@link java.util.LinkedList} is
53     adapted to support Queue, and a new non-thread-safe {@link
54     java.util.PriorityQueue} is added.
56     <h2>Threads</h2>
58 dl 1.13 Three minor changes are introduced to the {@link java.lang.Thread}
59     class:
60     <ul>
61     <li> It now allows per-thread installation of handlers for uncaught
62     exceptions. Ths optionally disassociates handlers from ThreadGroups,
63     which has proven to be too inflexible. (Note that the combination of
64     features in JSR-166 make ThreadGroups even less likely to be used in
65     most programs. Perhaps they will eventually be deprecated.)
67     <li> Access checks are no longer required when a Thread interrupts
68     <em>itself</em>. The <tt>interrupt</tt> method is the only way to
69     re-assert a thread's interruption status (and in the case of
70     self-interruption has no other effect than this). The check here
71     previously caused unjustifiable and uncontrollable failures when
72     restricted code invoked library code that must reassert interruption
73     to correctly propagate status when encountering some
74     <tt>InterruptedExceptions</tt>.
75     <li> The <tt>destroy</tt> method, which has never been implemented,
76     has finally been deprecated. This is just a spec change, reflecting
77     the fact that that the reason it has never been implmented is that
78     it was undesirable and unworkable.
79     </ul>
80 dl 1.9
81     <h2>Timing</h2>
83     Method <tt>nanoTime</tt> is added to {@link java.lang.System}. It
84     provides a high-precision timing facility that is distinct from and
85     uncoordinated with <tt>System.currentTimeMillis</tt>.
86 dl 1.8
87     <h2>Removing ThreadLocals</h2>
89 dl 1.9 The {@link java.lang.ThreadLocal} class now supports a means to remove
90     a ThreadLocal, which is needed in some thread-pool and worker-thread
91 dl 1.2 designs.
92 dl 1.9
94 tim 1.1
95     <hr>
96     </body>
97     </html>

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