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Tue Aug 5 14:36:04 2003 UTC (16 years, 3 months ago) by dl
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First pass getting ready for CR draft

1 tim 1.1 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
2     <html>
3     <head>
4 dl 1.9 <title>JSR 166 Community Review Draft Introduction.</title>
5 tim 1.1 </head>
6    
7     <body bgcolor="#ffffee" vlink="#0000aa" link="#cc0000">
8 dl 1.9 <h1>JJSR 166 Community Review Draft Introduction.</h1>
9 tim 1.1
10     by <a href="http://gee.cs.oswego.edu/dl">Doug Lea</a>
11     <p>
12    
13 dl 1.9 To chack for updates to this draft, access a preliminary prototype
14     release of main functionality, or join a mailing list discussing this
15     JSR, go to: <A
16     HREF="http://altair.cs.oswego.edu/mailman/listinfo/concurrency-interest">
17     http://altair.cs.oswego.edu/mailman/listinfo/concurrency-interest</A>
18     .
19 tim 1.1 <p>
20 dl 1.7
21 dl 1.9 <em> <b>Disclaimer</b>. The prototype implementation is experimental
22     code developed as part of JCP JSR-166 is made available to the
23     developer community for use as-is. It is not a supported product. Use
24     it at your own risk. The specification, language and implementation
25     are subject to change as a result of your feedback. Because these
26     features have not yet been approved for addition to the Java language,
27     there is no schedule for their inclusion in a product. </em>
28    
29     <p> <em> <b>Disclaimer</b>. This draft specification was produced
30     using JDK1.4 tools plus some preprocessing. The resulting javadocs do
31     not yet correctly render other planned JDK1.5 constructs on which
32     JSR-166 relies, most notably the use of generic types. We are
33     releasing this version now (before the availability of JDK1.5-based
34     tools) because, even though they are misformatted and sometimes lack
35     proper cross-referencing, they otherwise convey the intended
36     specifications. </em>
37    
38     <p> JSR-166 introduces package <tt>java.util.concurrent</tt>
39     containing utility classes commonly useful in concurrent
40     programming. Like package <tt>java.util</tt>, it includes a few small
41     standardized extensible frameworks, as well as some classes that
42     provide useful functionality and are otherwise tedious or difficult to
43     implement.
44    
45     <p>JSR-166 focusses on breadth, providing critical functionality
46     useful across a wide range of concurrent programming styles and
47     applications, ranging from low-level atomic operations, to
48     customizable locks and synchronization aids, to various concurrent
49     data structures, to high-level execution agents including thread
50     pools. This diversity reflects the range of contexts in which
51     developers of concurrent programs have been found to require or desire
52     support not previously available in J2SE, which also keeping the
53     resulting package small; providing only that minimial support for
54     which it makes sense to standardize.
55    
56     <p>Descriptions and brief motivations for the main components may be
57     found in the associated package documentation. JSR-166 also includes
58     a few changes and additions in packages outside of
59     java.util.concurrent. Here are brief descriptions.
60 tim 1.1
61     <h2>Queues</h2>
62    
63 dl 1.3 A basic (nonblocking) {@link java.util.Queue} interface extending
64 dl 1.9 {@link java.util.Collection} is introduced into
65     <tt>java.util</tt>. Existing class {@link java.util.LinkedList} is
66     adapted to support Queue, and a new non-thread-safe {@link
67     java.util.PriorityQueue} is added.
68    
69     <h2>Threads</h2>
70    
71     Two minor changes are introduced to the {@link java.lang.Thread}
72     class: It now allows per-thread installation of handlers for uncaught
73     exceptions. Ths optionally disassociates handlers from ThreadGroups,
74     which has proven to be too inflexible. (Note that the combination of
75     features in JSR-166 make ThreadGroups even less likely to be used in
76     most programs. Perhaps they will eventually be deprecated.) Secondly,
77     access checks are no longer required when a Thread interrupts
78     <em>itself</em>. The <tt>interrupt</tt> method is the only way to
79     re-assert a thread's interruption status (and in the case of
80     self-interruption has no other effect than this). The check here
81     previously caused unjustifiable and uncontrollable failures when
82     restricted code invoked library code that must reassert interruption
83     to correctly propagate status when encountering some
84     <tt>InterruptedExceptions</tt>.
85    
86     <h2>Timing</h2>
87    
88     Method <tt>nanoTime</tt> is added to {@link java.lang.System}. It
89     provides a high-precision timing facility that is distinct from and
90     uncoordinated with <tt>System.currentTimeMillis</tt>.
91 dl 1.8
92     <h2>Removing ThreadLocals</h2>
93    
94 dl 1.9 The {@link java.lang.ThreadLocal} class now supports a means to remove
95     a ThreadLocal, which is needed in some thread-pool and worker-thread
96 dl 1.2 designs.
97 dl 1.9
98    
99 tim 1.1
100     <hr>
101     <address><A HREF="http://gee.cs.oswego.edu/dl">Doug Lea</A></address>
102     </body>
103     </html>

dl@cs.oswego.edu
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