Package com.google.common.util.concurrent

Class AtomicLongMap<K>

  • All Implemented Interfaces:
    Serializable
    @GwtCompatible
public final class AtomicLongMap<K>
extends Object
implements Serializable
    A map containing long values that can be atomically updated. While writes to a traditional Map rely on put(K, V), the typical mechanism for writing to this map is addAndGet(K, long), which adds a long to the value currently associated with K. If a key has not yet been associated with a value, its implicit value is zero.

    Most methods in this class treat absent values and zero values identically, as individually documented. Exceptions to this are containsKey(java.lang.Object), size(), isEmpty(), asMap, and toString().

    Instances of this class may be used by multiple threads concurrently. All operations are atomic unless otherwise noted.

    Note: If your values are always positive and less than 2^31, you may wish to use a Multiset such as ConcurrentHashMultiset instead.

    Warning: Unlike Multiset, entries whose values are zero are not automatically removed from the map. Instead they must be removed manually with removeAllZeros().

    Since:
    11.0
    Author:
    Charles Fry
    See Also:
    Serialized Form

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      long addAndGet​(K key, long delta)
      Adds delta to the value currently associated with key, and returns the new value.
      Map<K,​Long> asMap()
      Returns a live, read-only view of the map backing this AtomicLongMap.
      void clear()
      Removes all of the mappings from this map.
      boolean containsKey​(Object key)
      Returns true if this map contains a mapping for the specified key.
      static <K> AtomicLongMap<K> create()
      Creates an AtomicLongMap.
      static <K> AtomicLongMap<K> create​(Map<? extends K,​? extends Long> m)
      Creates an AtomicLongMap with the same mappings as the specified Map.
      long decrementAndGet​(K key)
      Decrements by one the value currently associated with key, and returns the new value.
      long get​(K key)
      Returns the value associated with key, or zero if there is no value associated with key.
      long getAndAdd​(K key, long delta)
      Adds delta to the value currently associated with key, and returns the old value.
      long getAndDecrement​(K key)
      Decrements by one the value currently associated with key, and returns the old value.
      long getAndIncrement​(K key)
      Increments by one the value currently associated with key, and returns the old value.
      long incrementAndGet​(K key)
      Increments by one the value currently associated with key, and returns the new value.
      boolean isEmpty()
      Returns true if this map contains no key-value mappings.
      long put​(K key, long newValue)
      Associates newValue with key in this map, and returns the value previously associated with key, or zero if there was no such value.
      void putAll​(Map<? extends K,​? extends Long> m)
      Copies all of the mappings from the specified map to this map.
      long remove​(K key)
      Removes and returns the value associated with key.
      void removeAllZeros()
      Removes all mappings from this map whose values are zero.
      boolean removeIfZero​(K key)
      Atomically remove key from the map iff its associated value is 0.
      int size()
      Returns the number of key-value mappings in this map.
      long sum()
      Returns the sum of all values in this map.
      String toString()
      Returns a string representation of the object.

    • Method Detail

      • create

        public static <K> AtomicLongMap<K> create​(Map<? extends K,​? extends Long> m)
        Creates an AtomicLongMap with the same mappings as the specified Map.

      • get

        public long get​(K key)
        Returns the value associated with key, or zero if there is no value associated with key.

      • addAndGet

        @CanIgnoreReturnValue
public long addAndGet​(K key,
                      long delta)
        Adds delta to the value currently associated with key, and returns the new value.

      • getAndAdd

        @CanIgnoreReturnValue
public long getAndAdd​(K key,
                      long delta)
        Adds delta to the value currently associated with key, and returns the old value.

      • put

        @CanIgnoreReturnValue
public long put​(K key,
                long newValue)
        Associates newValue with key in this map, and returns the value previously associated with key, or zero if there was no such value.

      • putAll

        public void putAll​(Map<? extends K,​? extends Long> m)
        Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.

      • remove

        @CanIgnoreReturnValue
public long remove​(K key)
        Removes and returns the value associated with key. If key is not in the map, this method has no effect and returns zero.

      • removeAllZeros

        public void removeAllZeros()
        Removes all mappings from this map whose values are zero.

        This method is not atomic: the map may be visible in intermediate states, where some of the zero values have been removed and others have not.

      • sum

        public long sum()
        Returns the sum of all values in this map.

        This method is not atomic: the sum may or may not include other concurrent operations.

      • asMap

        public Map<K,​Long> asMap()
        Returns a live, read-only view of the map backing this AtomicLongMap.

      • containsKey

        public boolean containsKey​(Object key)
        Returns true if this map contains a mapping for the specified key.

      • size

        public int size()
        Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

      • isEmpty

        public boolean isEmpty()
        Returns true if this map contains no key-value mappings.

      • clear

        public void clear()
        Removes all of the mappings from this map. The map will be empty after this call returns.

        This method is not atomic: the map may not be empty after returning if there were concurrent writes.

      • toString

        public String toString()
        Description copied from class: java.lang.Object
        Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

        The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of: 

         getClass().getName() + '@' + Integer.toHexString(hashCode())
        Overrides:
        toString in class Object
        Returns:
        a string representation of the object.