Mercurial > hg > blitz_condensed
comparison src/EDU/oswego/cs/dl/util/concurrent/SynchronizedFloat.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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-1:000000000000 | 0:3dc0c5604566 |
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1 /* | |
2 File: SynchronizedFloat.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 19Jun1998 dl Create public version | |
12 */ | |
13 | |
14 package EDU.oswego.cs.dl.util.concurrent; | |
15 | |
16 /** | |
17 * A class useful for offloading synch for float instance variables. | |
18 * | |
19 * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>] | |
20 **/ | |
21 | |
22 public class SynchronizedFloat extends SynchronizedVariable implements Comparable, Cloneable { | |
23 | |
24 protected float value_; | |
25 | |
26 /** | |
27 * Make a new SynchronizedFloat with the given initial value, | |
28 * and using its own internal lock. | |
29 **/ | |
30 public SynchronizedFloat(float initialValue) { | |
31 super(); | |
32 value_ = initialValue; | |
33 } | |
34 | |
35 /** | |
36 * Make a new SynchronizedFloat with the given initial value, | |
37 * and using the supplied lock. | |
38 **/ | |
39 public SynchronizedFloat(float initialValue, Object lock) { | |
40 super(lock); | |
41 value_ = initialValue; | |
42 } | |
43 | |
44 /** | |
45 * Return the current value | |
46 **/ | |
47 public final float get() { synchronized(lock_) { return value_; } } | |
48 | |
49 /** | |
50 * Set to newValue. | |
51 * @return the old value | |
52 **/ | |
53 | |
54 public float set(float newValue) { | |
55 synchronized (lock_) { | |
56 float old = value_; | |
57 value_ = newValue; | |
58 return old; | |
59 } | |
60 } | |
61 | |
62 /** | |
63 * Set value to newValue only if it is currently assumedValue. | |
64 * @return true if successful | |
65 **/ | |
66 public boolean commit(float assumedValue, float newValue) { | |
67 synchronized(lock_) { | |
68 boolean success = (assumedValue == value_); | |
69 if (success) value_ = newValue; | |
70 return success; | |
71 } | |
72 } | |
73 | |
74 | |
75 /** | |
76 * Atomically swap values with another SynchronizedFloat. | |
77 * Uses identityHashCode to avoid deadlock when | |
78 * two SynchronizedFloats attempt to simultaneously swap with each other. | |
79 * (Note: Ordering via identyHashCode is not strictly guaranteed | |
80 * by the language specification to return unique, orderable | |
81 * values, but in practice JVMs rely on them being unique.) | |
82 * @return the new value | |
83 **/ | |
84 | |
85 public float swap(SynchronizedFloat other) { | |
86 if (other == this) return get(); | |
87 SynchronizedFloat fst = this; | |
88 SynchronizedFloat snd = other; | |
89 if (System.identityHashCode(fst) > System.identityHashCode(snd)) { | |
90 fst = other; | |
91 snd = this; | |
92 } | |
93 synchronized(fst.lock_) { | |
94 synchronized(snd.lock_) { | |
95 fst.set(snd.set(fst.get())); | |
96 return get(); | |
97 } | |
98 } | |
99 } | |
100 | |
101 | |
102 /** | |
103 * Add amount to value (i.e., set value += amount) | |
104 * @return the new value | |
105 **/ | |
106 public float add(float amount) { | |
107 synchronized (lock_) { | |
108 return value_ += amount; | |
109 } | |
110 } | |
111 | |
112 /** | |
113 * Subtract amount from value (i.e., set value -= amount) | |
114 * @return the new value | |
115 **/ | |
116 public float subtract(float amount) { | |
117 synchronized (lock_) { | |
118 return value_ -= amount; | |
119 } | |
120 } | |
121 | |
122 /** | |
123 * Multiply value by factor (i.e., set value *= factor) | |
124 * @return the new value | |
125 **/ | |
126 public synchronized float multiply(float factor) { | |
127 synchronized (lock_) { | |
128 return value_ *= factor; | |
129 } | |
130 } | |
131 | |
132 /** | |
133 * Divide value by factor (i.e., set value /= factor) | |
134 * @return the new value | |
135 **/ | |
136 public float divide(float factor) { | |
137 synchronized (lock_) { | |
138 return value_ /= factor; | |
139 } | |
140 } | |
141 | |
142 public int compareTo(float other) { | |
143 float val = get(); | |
144 return (val < other)? -1 : (val == other)? 0 : 1; | |
145 } | |
146 | |
147 public int compareTo(SynchronizedFloat other) { | |
148 return compareTo(other.get()); | |
149 } | |
150 | |
151 public int compareTo(Object other) { | |
152 return compareTo((SynchronizedFloat)other); | |
153 } | |
154 | |
155 public boolean equals(Object other) { | |
156 if (other != null && | |
157 other instanceof SynchronizedFloat) | |
158 return get() == ((SynchronizedFloat)other).get(); | |
159 else | |
160 return false; | |
161 } | |
162 | |
163 public int hashCode() { | |
164 return Float.floatToIntBits(get()); | |
165 } | |
166 | |
167 public String toString() { return String.valueOf(get()); } | |
168 | |
169 } | |
170 |