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comparison src/EDU/oswego/cs/dl/util/concurrent/SynchronizedFloat.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: 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