src/jsr166e/LongAdderTable.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package jsr166e;
import jsr166e.LongAdder;
import java.util.Map;
import java.util.Set;
import java.io.Serializable;

/**
 * A keyed table of adders, that may be useful in computing frequency
 * counts and histograms, or may be used a form of multiset.  A {@link
 * LongAdder} is associated with each key. Keys are added to the table
 * implicitly upon any attempt to update, or may be added explicitly
 * using method {@link #install}.
 *
 * <p><em>jsr166e note: This class is targeted to be placed in
 * java.util.concurrent.atomic<em>
 *
 * @since 1.8
 * @author Doug Lea
 */
public class LongAdderTable<K> implements Serializable {
    /** Relies on default serialization */
    private static final long serialVersionUID = 7249369246863182397L;

    /** The underlying map */
    private final ConcurrentHashMapV8<K, LongAdder> map;

    static final class CreateAdder
        implements ConcurrentHashMapV8.MappingFunction<Object, LongAdder> {
        public LongAdder map(Object unused) { return new LongAdder(); }
    }

    private static final CreateAdder createAdder = new CreateAdder();

    /**
     * Creates a new empty table.
     */
    public LongAdderTable() {
        map = new ConcurrentHashMapV8<K, LongAdder>();
    }

    /**
     * If the given key does not already exist in the table, inserts
     * the key with initial sum of zero; in either case returning the
     * adder associated with this key.
     *
     * @param key the key
     * @return the adder associated with the key
     */
    public LongAdder install(K key) {
        return map.computeIfAbsent(key, createAdder);
    }

    /**
     * Adds the given value to the sum associated with the given
     * key.  If the key does not already exist in the table, it is
     * inserted.
     *
     * @param key the key
     * @param x the value to add
     */
    public void add(K key, long x) {
        map.computeIfAbsent(key, createAdder).add(x);
    }

    /**
     * Increments the sum associated with the given key.  If the key
     * does not already exist in the table, it is inserted.
     *
     * @param key the key
     */
    public void increment(K key) { add(key, 1L); }

    /**
     * Decrements the sum associated with the given key.  If the key
     * does not already exist in the table, it is inserted.
     *
     * @param key the key
     */
    public void decrement(K key) { add(key, -1L); }

    /**
     * Returns the sum associated with the given key, or zero if the
     * key does not currently exist in the table.
     *
     * @param key the key
     * @return the sum associated with the key, or zero if the key is
     * not in the table
     */
    public long sum(K key) {
        LongAdder a = map.get(key);
        return a == null ? 0L : a.sum();
    }

    /**
     * Resets the sum associated with the given key to zero if the key
     * exists in the table.  This method does <em>NOT</em> add or
     * remove the key from the table (see {@link #remove}).
     *
     * @param key the key
     */
    public void reset(K key) {
        LongAdder a = map.get(key);
        if (a != null)
            a.reset();
    }

    /**
     * Resets the sum associated with the given key to zero if the key
     * exists in the table.  This method does <em>NOT</em> add or
     * remove the key from the table (see {@link #remove}).
     *
     * @param key the key
     * @return the previous sum, or zero if the key is not
     * in the table
     */
    public long sumThenReset(K key) {
        LongAdder a = map.get(key);
        return a == null ? 0L : a.sumThenReset();
    }

    /**
     * Returns the sum totalled across all keys.
     *
     * @return the sum totalled across all keys
     */
    public long sumAll() {
        long sum = 0L;
        for (LongAdder a : map.values())
            sum += a.sum();
        return sum;
    }

    /**
     * Resets the sum associated with each key to zero.
     */
    public void resetAll() {
        for (LongAdder a : map.values())
            a.reset();
    }

    /**
     * Totals, then resets, the sums associated with all keys.
     *
     * @return the sum totalled across all keys
     */
    public long sumThenResetAll() {
        long sum = 0L;
        for (LongAdder a : map.values())
            sum += a.sumThenReset();
        return sum;
    }

    /**
     * Removes the given key from the table.
     *
     * @param key the key
     */
    public void remove(K key) { map.remove(key); }

    /**
     * Removes all keys from the table.
     */
    public void removeAll() { map.clear(); }

    /**
     * Returns the current set of keys.
     *
     * @return the current set of keys
     */
    public Set<K> keySet() {
        return map.keySet();
    }

    /**
     * Returns the current set of key-value mappings.
     *
     * @return the current set of key-value mappings
     */
    public Set<Map.Entry<K,LongAdder>> entrySet() {
        return map.entrySet();
    }

}
Revision:	1.7
Committed:	Sun Oct 2 22:01:06 2011 UTC (12 years, 7 months ago) by dl
Branch:	MAIN
Changes since 1.6:	+2 -11 lines
Log Message:	Reparameterize compute method; various other improvements
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/publicdomain/zero/1.0/
5			*/
6
7	dl	1.2	package jsr166e;
8	dl	1.1	import jsr166e.LongAdder;
9			import java.util.Map;
10			import java.util.Set;
11			import java.io.Serializable;
12
13			/**
14			* A keyed table of adders, that may be useful in computing frequency
15			* counts and histograms, or may be used a form of multiset. A {@link
16			* LongAdder} is associated with each key. Keys are added to the table
17			* implicitly upon any attempt to update, or may be added explicitly
18			* using method {@link #install}.
19			*
20			* <p><em>jsr166e note: This class is targeted to be placed in
21			* java.util.concurrent.atomic<em>
22			*
23	jsr166	1.5	* @since 1.8
24	dl	1.1	* @author Doug Lea
25			*/
26			public class LongAdderTable<K> implements Serializable {
27			/** Relies on default serialization */
28			private static final long serialVersionUID = 7249369246863182397L;
29
30	dl	1.3	/** The underlying map */
31			private final ConcurrentHashMapV8<K, LongAdder> map;
32
33	jsr166	1.4	static final class CreateAdder
34	dl	1.3	implements ConcurrentHashMapV8.MappingFunction<Object, LongAdder> {
35			public LongAdder map(Object unused) { return new LongAdder(); }
36			}
37	dl	1.1
38	dl	1.3	private static final CreateAdder createAdder = new CreateAdder();
39	dl	1.1
40			/**
41			* Creates a new empty table.
42			*/
43			public LongAdderTable() {
44	dl	1.3	map = new ConcurrentHashMapV8<K, LongAdder>();
45	dl	1.1	}
46
47			/**
48			* If the given key does not already exist in the table, inserts
49			* the key with initial sum of zero; in either case returning the
50			* adder associated with this key.
51			*
52			* @param key the key
53			* @return the adder associated with the key
54			*/
55			public LongAdder install(K key) {
56	dl	1.7	return map.computeIfAbsent(key, createAdder);
57	dl	1.1	}
58
59			/**
60			* Adds the given value to the sum associated with the given
61			* key. If the key does not already exist in the table, it is
62			* inserted.
63			*
64			* @param key the key
65			* @param x the value to add
66			*/
67			public void add(K key, long x) {
68	dl	1.7	map.computeIfAbsent(key, createAdder).add(x);
69	dl	1.1	}
70
71			/**
72			* Increments the sum associated with the given key. If the key
73			* does not already exist in the table, it is inserted.
74			*
75			* @param key the key
76			*/
77			public void increment(K key) { add(key, 1L); }
78
79			/**
80			* Decrements the sum associated with the given key. If the key
81			* does not already exist in the table, it is inserted.
82			*
83			* @param key the key
84			*/
85			public void decrement(K key) { add(key, -1L); }
86
87			/**
88			* Returns the sum associated with the given key, or zero if the
89			* key does not currently exist in the table.
90			*
91			* @param key the key
92			* @return the sum associated with the key, or zero if the key is
93			* not in the table
94			*/
95			public long sum(K key) {
96			LongAdder a = map.get(key);
97			return a == null ? 0L : a.sum();
98			}
99
100			/**
101			* Resets the sum associated with the given key to zero if the key
102			* exists in the table. This method does <em>NOT</em> add or
103			* remove the key from the table (see {@link #remove}).
104			*
105			* @param key the key
106			*/
107			public void reset(K key) {
108			LongAdder a = map.get(key);
109			if (a != null)
110			a.reset();
111			}
112
113			/**
114			* Resets the sum associated with the given key to zero if the key
115			* exists in the table. This method does <em>NOT</em> add or
116			* remove the key from the table (see {@link #remove}).
117			*
118			* @param key the key
119			* @return the previous sum, or zero if the key is not
120			* in the table
121			*/
122			public long sumThenReset(K key) {
123			LongAdder a = map.get(key);
124			return a == null ? 0L : a.sumThenReset();
125			}
126
127			/**
128			* Returns the sum totalled across all keys.
129			*
130	jsr166	1.6	* @return the sum totalled across all keys
131	dl	1.1	*/
132			public long sumAll() {
133			long sum = 0L;
134			for (LongAdder a : map.values())
135			sum += a.sum();
136			return sum;
137			}
138
139			/**
140			* Resets the sum associated with each key to zero.
141			*/
142			public void resetAll() {
143			for (LongAdder a : map.values())
144			a.reset();
145			}
146
147			/**
148			* Totals, then resets, the sums associated with all keys.
149			*
150	jsr166	1.6	* @return the sum totalled across all keys
151	dl	1.1	*/
152			public long sumThenResetAll() {
153			long sum = 0L;
154			for (LongAdder a : map.values())
155			sum += a.sumThenReset();
156			return sum;
157			}
158
159			/**
160			* Removes the given key from the table.
161			*
162			* @param key the key
163			*/
164			public void remove(K key) { map.remove(key); }
165
166			/**
167			* Removes all keys from the table.
168			*/
169			public void removeAll() { map.clear(); }
170
171			/**
172			* Returns the current set of keys.
173			*
174			* @return the current set of keys
175			*/
176			public Set<K> keySet() {
177			return map.keySet();
178			}
179
180			/**
181			* Returns the current set of key-value mappings.
182			*
183			* @return the current set of key-value mappings
184			*/
185			public Set<Map.Entry<K,LongAdder>> entrySet() {
186			return map.entrySet();
187			}
188
189			}