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## com.google.common.util.concurrent
Class AtomicLongMap<K>

    java.lang.Object
      com.google.common.util.concurrent.AtomicLongMap<K>

    @Beta
    @GwtCompatible
    public final class AtomicLongMap<K>

extends Object

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

Method Summary
`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.
`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()`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Method Detail

### create

    public static <K> AtomicLongMap<K> create()

  Creates an `AtomicLongMap`.

### 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`.

### incrementAndGet

    public long incrementAndGet(K key)

  Increments by one the value currently associated with `key`, and returns the new value.

### decrementAndGet

    public long decrementAndGet(K key)

  Decrements by one the value currently associated with `key`, and returns the new value.

### addAndGet

    public long addAndGet(K key,
                          long delta)

  Adds `delta` to the value currently associated with `key`, and returns the new value.

### getAndIncrement

    public long getAndIncrement(K key)

  Increments by one the value currently associated with `key`, and returns the old value.

### getAndDecrement

    public long getAndDecrement(K key)

  Decrements by one the value currently associated with `key`, and returns the old value.

### getAndAdd

    public long getAndAdd(K key,
                          long delta)

  Adds `delta` to the value currently associated with `key`, and returns the old value.

### put

    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

    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()

  Overrides:
    `toString` in class `Object`

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