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 as 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.Fun<Object, LongAdder> {
        public LongAdder apply(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:	1.11
Committed:	Sun Jan 18 20:17:33 2015 UTC (9 years, 3 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.10:	+1 -0 lines
Log Message:	exactly one blank line before and after package statements
#	Content
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	package jsr166e;
8
9	import jsr166e.LongAdder;
10	import java.util.Map;
11	import java.util.Set;
12	import java.io.Serializable;
13
14	/**
15	* A keyed table of adders, that may be useful in computing frequency
16	* counts and histograms, or may be used as a form of multiset. A
17	* {@link LongAdder} is associated with each key. Keys are added to
18	* the table implicitly upon any attempt to update, or may be added
19	* explicitly using method {@link #install}.
20	*
21	* <p><em>jsr166e note: This class is targeted to be placed in
22	* java.util.concurrent.atomic.</em>
23	*
24	* @since 1.8
25	* @author Doug Lea
26	*/
27	public class LongAdderTable<K> implements Serializable {
28	/** Relies on default serialization */
29	private static final long serialVersionUID = 7249369246863182397L;
30
31	/** The underlying map */
32	private final ConcurrentHashMapV8<K, LongAdder> map;
33
34	static final class CreateAdder
35	implements ConcurrentHashMapV8.Fun<Object, LongAdder> {
36	public LongAdder apply(Object unused) { return new LongAdder(); }
37	}
38
39	private static final CreateAdder createAdder = new CreateAdder();
40
41	/**
42	* Creates a new empty table.
43	*/
44	public LongAdderTable() {
45	map = new ConcurrentHashMapV8<K, LongAdder>();
46	}
47
48	/**
49	* If the given key does not already exist in the table, inserts
50	* the key with initial sum of zero; in either case returning the
51	* adder associated with this key.
52	*
53	* @param key the key
54	* @return the adder associated with the key
55	*/
56	public LongAdder install(K key) {
57	return map.computeIfAbsent(key, createAdder);
58	}
59
60	/**
61	* Adds the given value to the sum associated with the given
62	* key. If the key does not already exist in the table, it is
63	* inserted.
64	*
65	* @param key the key
66	* @param x the value to add
67	*/
68	public void add(K key, long x) {
69	map.computeIfAbsent(key, createAdder).add(x);
70	}
71
72	/**
73	* Increments the sum associated with the given key. If the key
74	* does not already exist in the table, it is inserted.
75	*
76	* @param key the key
77	*/
78	public void increment(K key) { add(key, 1L); }
79
80	/**
81	* Decrements the sum associated with the given key. If the key
82	* does not already exist in the table, it is inserted.
83	*
84	* @param key the key
85	*/
86	public void decrement(K key) { add(key, -1L); }
87
88	/**
89	* Returns the sum associated with the given key, or zero if the
90	* key does not currently exist in the table.
91	*
92	* @param key the key
93	* @return the sum associated with the key, or zero if the key is
94	* not in the table
95	*/
96	public long sum(K key) {
97	LongAdder a = map.get(key);
98	return a == null ? 0L : a.sum();
99	}
100
101	/**
102	* Resets the sum associated with the given key to zero if the key
103	* exists in the table. This method does <em>NOT</em> add or
104	* remove the key from the table (see {@link #remove}).
105	*
106	* @param key the key
107	*/
108	public void reset(K key) {
109	LongAdder a = map.get(key);
110	if (a != null)
111	a.reset();
112	}
113
114	/**
115	* Resets the sum associated with the given key to zero if the key
116	* exists in the table. This method does <em>NOT</em> add or
117	* remove the key from the table (see {@link #remove}).
118	*
119	* @param key the key
120	* @return the previous sum, or zero if the key is not
121	* in the table
122	*/
123	public long sumThenReset(K key) {
124	LongAdder a = map.get(key);
125	return a == null ? 0L : a.sumThenReset();
126	}
127
128	/**
129	* Returns the sum totalled across all keys.
130	*
131	* @return the sum totalled across all keys
132	*/
133	public long sumAll() {
134	long sum = 0L;
135	for (LongAdder a : map.values())
136	sum += a.sum();
137	return sum;
138	}
139
140	/**
141	* Resets the sum associated with each key to zero.
142	*/
143	public void resetAll() {
144	for (LongAdder a : map.values())
145	a.reset();
146	}
147
148	/**
149	* Totals, then resets, the sums associated with all keys.
150	*
151	* @return the sum totalled across all keys
152	*/
153	public long sumThenResetAll() {
154	long sum = 0L;
155	for (LongAdder a : map.values())
156	sum += a.sumThenReset();
157	return sum;
158	}
159
160	/**
161	* Removes the given key from the table.
162	*
163	* @param key the key
164	*/
165	public void remove(K key) { map.remove(key); }
166
167	/**
168	* Removes all keys from the table.
169	*/
170	public void removeAll() { map.clear(); }
171
172	/**
173	* Returns the current set of keys.
174	*
175	* @return the current set of keys
176	*/
177	public Set<K> keySet() {
178	return map.keySet();
179	}
180
181	/**
182	* Returns the current set of key-value mappings.
183	*
184	* @return the current set of key-value mappings
185	*/
186	public Set<Map.Entry<K,LongAdder>> entrySet() {
187	return map.entrySet();
188	}
189
190	}