io.vertx.core.shareddata

## Interface LocalMap<K,V>

- All Superinterfaces:
    Map<K,V>

      public interface LocalMap<K,V>
      extends Map<K,V>

  Local maps can be used to share data safely in a single Vert.x instance.

  By default the map allows immutable keys and values. Custom keys and values should implement `Shareable` interface. The map returns their copies.

  This ensures there is no shared access to mutable state from different threads (e.g. different event loops) in the Vert.x instance, and means you don't have to protect access to that state using synchronization or locks.

  Since the version 3.4, this class extends the `Map` interface. However some methods are only accessible in Java.

  Author:
    Tim Fox
  See Also:
    `Shareable`

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from interface java.util.Map

      `Map.Entry<K,V>`

  - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `clear()` Clear all entries in the map
    `void` | `close()` Close and release the map
    `V` | `compute(K key, java.util.function.BiFunction<? super K,? super V,? extends V> remappingFunction)` Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
    `V` | `computeIfAbsent(K key, java.util.function.Function<? super K,? extends V> mappingFunction)` If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
    `V` | `computeIfPresent(K key, java.util.function.BiFunction<? super K,? super V,? extends V> remappingFunction)` If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
    `boolean` | `containsKey(Object key)` Returns `true` if this map contains a mapping for the specified key.
    `boolean` | `containsValue(Object value)` Returns @{code true} if this map maps one or more keys to the specified value.
    `Set<Map.Entry<K,V>>` | `entrySet()` Returns a `Set` view of the mappings contained in this map.
    `void` | `forEach(java.util.function.BiConsumer<? super K,? super V> action)` Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
    `V` | `get(Object key)` Get a value from the map
    `V` | `getOrDefault(Object key, V defaultValue)` Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
    `boolean` | `isEmpty()`
    `Set<K>` | `keySet()`
    `V` | `merge(K key, V value, java.util.function.BiFunction<? super V,? super V,? extends V> remappingFunction)` If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
    `V` | `put(K key, V value)` Put an entry in the map
    `void` | `putAll(Map<? extends K,? extends V> m)` Copies all of the mappings from the specified map to this map.
    `V` | `putIfAbsent(K key, V value)` Put the entry only if there is no existing entry for that key
    `V` | `remove(Object key)` Remove an entry from the map
    `boolean` | `remove(Object key, Object value)` Removes the entry for the specified key only if it is currently mapped to the specified value.
    `boolean` | `removeIfPresent(K key, V value)` Remove the entry only if there is an entry with the specified key and value.
    `V` | `replace(K key, V value)` Replace the entry only if there is an existing entry with the key
    `boolean` | `replace(K key, V oldValue, V newValue)` Replaces the entry for the specified key only if currently mapped to the specified value.
    `void` | `replaceAll(java.util.function.BiFunction<? super K,? super V,? extends V> function)` Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
    `boolean` | `replaceIfPresent(K key, V oldValue, V newValue)` Replace the entry only if there is an existing entry with the specified key and value.
    `int` | `size()` Get the size of the map
    `Collection<V>` | `values()`

    - ### Methods inherited from interface java.util.Map

      `equals, hashCode`

- - ### Method Detail

    - #### get

          V get(Object key)

      Get a value from the map
      Specified by:
        `get` in interface `Map<K,V>`
      Parameters:
        `key` - the key
      Returns:
        the value, or null if none

    - #### put

          V put(K key,
                V value)

      Put an entry in the map
      Specified by:
        `put` in interface `Map<K,V>`
      Parameters:
        `key` - the key
        `value` - the value
      Returns:
        return the old value, or null if none

    - #### remove

          V remove(Object key)

      Remove an entry from the map
      Specified by:
        `remove` in interface `Map<K,V>`
      Parameters:
        `key` - the key
      Returns:
        the old value

    - #### clear

          void clear()

      Clear all entries in the map
      Specified by:
        `clear` in interface `Map<K,V>`

    - #### size

          int size()

      Get the size of the map
      Specified by:
        `size` in interface `Map<K,V>`
      Returns:
        the number of entries in the map

    - #### isEmpty

          boolean isEmpty()

      Specified by:
        `isEmpty` in interface `Map<K,V>`
      Returns:
        true if there are zero entries in the map

    - #### putIfAbsent

          V putIfAbsent(K key,
                        V value)

      Put the entry only if there is no existing entry for that key
      Specified by:
        `putIfAbsent` in interface `Map<K,V>`
      Parameters:
        `key` - the key
        `value` - the value
      Returns:
        the old value or null, if none

    - #### removeIfPresent

          boolean removeIfPresent(K key,
                                  V value)

      Remove the entry only if there is an entry with the specified key and value.

      This method is the poyglot version of `remove(Object, Object)`.

      Parameters:
        `key` - the key
        `value` - the value
      Returns:
        true if removed

    - #### replaceIfPresent

          boolean replaceIfPresent(K key,
                                   V oldValue,
                                   V newValue)

      Replace the entry only if there is an existing entry with the specified key and value.

      This method is the polyglot version of `replace(Object, Object, Object)`.

      Parameters:
        `key` - the key
        `oldValue` - the old value
        `newValue` - the new value
      Returns:
        true if removed

    - #### replace

          V replace(K key,
                    V value)

      Replace the entry only if there is an existing entry with the key
      Specified by:
        `replace` in interface `Map<K,V>`
      Parameters:
        `key` - the key
        `value` - the new value
      Returns:
        the old value

    - #### close

          void close()

      Close and release the map

    - #### keySet

          Set<K> keySet()

      Specified by:
        `keySet` in interface `Map<K,V>`
      Returns:
        the set of keys in the map

    - #### values

          Collection<V> values()

      Specified by:
        `values` in interface `Map<K,V>`
      Returns:
        the set of values in the map

    - #### compute

          V compute(K key,
                    java.util.function.BiFunction<? super K,? super V,? extends V> remappingFunction)

      Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).

      If the function returns `null`, the mapping is removed (or remains absent if initially absent). If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

      Specified by:
        `compute` in interface `Map<K,V>`
      Parameters:
        `key` - key with which the specified value is to be associated
        `remappingFunction` - the function to compute a value
      Returns:
        the new value associated with the specified key, or null if none

    - #### computeIfAbsent

          V computeIfAbsent(K key,
                            java.util.function.Function<? super K,? extends V> mappingFunction)

      If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.

      If the function returns `null` no mapping is recorded. If the function itself throws an (unchecked) exception, the exception is rethrown, and no mapping is recorded.

      Specified by:
        `computeIfAbsent` in interface `Map<K,V>`
      Parameters:
        `key` - key with which the specified value is to be associated
        `mappingFunction` - the function to compute a value
      Returns:
        the current (existing or computed) value associated with the specified key, or null if the computed value is null

    - #### computeIfPresent

          V computeIfPresent(K key,
                             java.util.function.BiFunction<? super K,? super V,? extends V> remappingFunction)

      If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.

      If the function returns `null`, the mapping is removed. If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

      Specified by:
        `computeIfPresent` in interface `Map<K,V>`
      Parameters:
        `key` - key with which the specified value is to be associated
        `remappingFunction` - the function to compute a value
      Returns:
        the new value associated with the specified key, or null if none

    - #### containsKey

          boolean containsKey(Object key)

      Returns `true` if this map contains a mapping for the specified key.
      Specified by:
        `containsKey` in interface `Map<K,V>`
      Parameters:
        `key` - key whose presence in this map is to be tested
      Returns:
        `true` if this map contains a mapping for the specified key

    - #### containsValue

          boolean containsValue(Object value)

      Returns @{code true} if this map maps one or more keys to the specified value.
      Specified by:
        `containsValue` in interface `Map<K,V>`
      Parameters:
        `value` - value whose presence in this map is to be tested
      Returns:
        @{code true} if this map maps one or more keys to the specified value

    - #### entrySet

          Set<Map.Entry<K,V>> entrySet()

      Returns a `Set` view of the mappings contained in this map.

      Unlike the default `Map` implementation, the set is not backed by the map. So changes made to the map are not reflected in the set. Entries added or remove to the set are not reflected to the map. In addition, the entries are not modifiable (`Map.Entry.setValue(Object)` is not supported).

      Specified by:
        `entrySet` in interface `Map<K,V>`
      Returns:
        a set view of the mappings contained in this map

    - #### forEach

          void forEach(java.util.function.BiConsumer<? super K,? super V> action)

      Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.

      Exceptions thrown by the action are relayed to the caller.

      Specified by:
        `forEach` in interface `Map<K,V>`
      Parameters:
        `action` - The action to be performed for each entry

    - #### getOrDefault

          V getOrDefault(Object key,
                         V defaultValue)

      Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
      Specified by:
        `getOrDefault` in interface `Map<K,V>`
      Parameters:
        `key` - the key whose associated value is to be returned
        `defaultValue` - the default mapping of the key
      Returns:
        the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key

    - #### merge

          V merge(K key,
                  V value,
                  java.util.function.BiFunction<? super V,? super V,? extends V> remappingFunction)

      If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result is `null`. This method may be of use when combining multiple mapped values for a key.
      Specified by:
        `merge` in interface `Map<K,V>`
      Parameters:
        `key` - key with which the resulting value is to be associated
        `value` - the non-null value to be merged with the existing value associated with the key or, if no existing value or a null value is associated with the key, to be associated with the key
        `remappingFunction` - the function to recompute a value if present
      Returns:
        the new value associated with the specified key, or null if no value is associated with the key

    - #### putAll

          void putAll(Map<? extends K,? extends V> 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.
      Specified by:
        `putAll` in interface `Map<K,V>`
      Parameters:
        `m` - mappings to be stored in this map

    - #### remove

          boolean remove(Object key,
                         Object value)

      Removes the entry for the specified key only if it is currently mapped to the specified value.
      Specified by:
        `remove` in interface `Map<K,V>`
      Parameters:
        `key` - key with which the specified value is associated
        `value` - value expected to be associated with the specified key
      Returns:
        `true` if the value was removed

    - #### replace

          boolean replace(K key,
                          V oldValue,
                          V newValue)

      Replaces the entry for the specified key only if currently mapped to the specified value.
      Specified by:
        `replace` in interface `Map<K,V>`
      Parameters:
        `key` - key with which the specified value is associated
        `oldValue` - value expected to be associated with the specified key
        `newValue` - value to be associated with the specified key
      Returns:
        `true` if the value was replaced

    - #### replaceAll

          void replaceAll(java.util.function.BiFunction<? super K,? super V,? extends V> function)

      Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. Exceptions thrown by the function are relayed to the caller.
      Specified by:
        `replaceAll` in interface `Map<K,V>`
      Parameters:
        `function` - the function to apply to each entry

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