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comparison src/EDU/oswego/cs/dl/util/concurrent/Slot.java @ 0:3dc0c5604566

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Initial checkin of blitz 2.0 fcs - no installer yet.
author Dan Creswell <dan.creswell@gmail.com>
date Sat, 21 Mar 2009 11:00:06 +0000
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1 /*
2 File: Slot.java
3
4 Originally written by Doug Lea and released into the public domain.
5 This may be used for any purposes whatsoever without acknowledgment.
6 Thanks for the assistance and support of Sun Microsystems Labs,
7 and everyone contributing, testing, and using this code.
8
9 History:
10 Date Who What
11 11Jun1998 dl Create public version
12 25aug1998 dl added peek
13 */
14
15 package EDU.oswego.cs.dl.util.concurrent;
16 import java.lang.reflect.*;
17
18 /**
19 * A one-slot buffer, using semaphores to control access.
20 * Slots are usually more efficient and controllable than using other
21 * bounded buffers implementations with capacity of 1.
22 * <p>
23 * Among other applications, Slots can be convenient in token-passing
24 * designs: Here. the Slot holds a some object serving as a token,
25 * that can be obtained
26 * and returned by various threads.
27 *
28 * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>]
29 **/
30
31 public class Slot extends SemaphoreControlledChannel {
32
33 /**
34 * Create a buffer with the given capacity, using
35 * the supplied Semaphore class for semaphores.
36 * @exception NoSuchMethodException If class does not have constructor
37 * that intializes permits
38 * @exception SecurityException if constructor information
39 * not accessible
40 * @exception InstantiationException if semaphore class is abstract
41 * @exception IllegalAccessException if constructor cannot be called
42 * @exception InvocationTargetException if semaphore constructor throws an
43 * exception
44 **/
45
46 public Slot(Class semaphoreClass)
47 throws NoSuchMethodException,
48 SecurityException,
49 InstantiationException,
50 IllegalAccessException,
51 InvocationTargetException {
52 super(1, semaphoreClass);
53 }
54
55 /**
56 * Create a new Slot using default Semaphore implementations
57 **/
58 public Slot() {
59 super(1);
60 }
61
62 /** The slot **/
63 protected Object item_ = null;
64
65
66 /** Set the item in preparation for a take **/
67 protected synchronized void insert(Object x) {
68 item_ = x;
69 }
70
71 /** Take item known to exist **/
72 protected synchronized Object extract() {
73 Object x = item_;
74 item_ = null;
75 return x;
76 }
77
78 public synchronized Object peek() {
79 return item_;
80 }
81
82 }