Package com.tangosol.util

Class AbstractKeyBasedMap<K,V>

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.AbstractKeyBasedMap<K,V>
All Implemented Interfaces:
Map<K,V>
Direct Known Subclasses:
AbstractKeySetBasedMap, CacheStoreMap.ReadWriteMap, KeyValueArrayMap, OpenHashMap, PartitionSplittingBackingMap, PartitionSplittingBackingMap.MaskedPartitionMap, ReadWriteBackingMap.EvictingBackupMap, SimpleOverflowMap, SimpleSerializationMap
public abstract class AbstractKeyBasedMap<K,V> extends Base implements Map<K,V>
AbstractKeyBasedMap is a base class for Map implementations. The primary difference between the AbstractMap abstract class and this abstract class is this: that AbstractMap requires a sub-class to provide an Entry Set implementation, while AbstractKeyBasedMap requires a read-only sub-class to implement only get() and iterateKeys(), and a read-write sub-class to additionally implement only put() and remove().

Read-only implementations must implement iterateKeys() and get(Object). Read/write implementations must additionally implement put(Object, Object) and remove(Object). A number of the methods have implementations provided, but are extremely inefficient for Maps that contain large amounts of data, including clear(), containsKey(Object), size() (and by extension isEmpty()). Furthermore, if any of a number of method implementations has any cost of returning an "old value", such as is done by the put(K, V) and remove(Object) methods, then the putAll(java.util.Map) and removeBlind(Object) methods should also be implemented.

Author:
2005.07.13 cp

  • Constructor Details

    • AbstractKeyBasedMap

      public AbstractKeyBasedMap()

  • Method Details

    • clear

      public void clear()
      Clear all key/value mappings.
      Specified by:
      clear in interface Map<K,V>

    • containsKey

      public boolean containsKey(Object oKey)
      Returns true if this map contains a mapping for the specified key.
      Specified by:
      containsKey in interface Map<K,V>
      Returns:
      true if this map contains a mapping for the specified key, false otherwise.

    • containsValue

      public boolean containsValue(Object oValue)
      Returns true if this Map maps one or more keys to the specified value.
      Specified by:
      containsValue in interface Map<K,V>
      Returns:
      true if this Map maps one or more keys to the specified value, false otherwise

    • entrySet

      public Set<Map.Entry<K,V>> entrySet()
      Returns a set view of the mappings contained in this map. Each element in the returned set is an Map.Entry. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except by the iterator's own remove operation, or by the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It is not expected to support the add or addAll operations.
      Specified by:
      entrySet in interface Map<K,V>
      Returns:
      a set view of the mappings contained in this map

    • get

      public abstract V get(Object oKey)
      Returns the value to which this map maps the specified key.
      Specified by:
      get in interface Map<K,V>
      Parameters:
      oKey - the key object
      Returns:
      the value to which this map maps the specified key, or null if the map contains no mapping for this key

    • isEmpty

      public boolean isEmpty()
      Returns true if this map contains no key-value mappings.
      Specified by:
      isEmpty in interface Map<K,V>
      Returns:
      true if this map contains no key-value mappings

    • keySet

      public Set<K> keySet()
      Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll retainAll, and clear operations. It is not expected to support the add or addAll operations.
      Specified by:
      keySet in interface Map<K,V>
      Returns:
      a set view of the keys contained in this map

    • put

      public V put(K oKey, V oValue)
      Associates the specified value with the specified key in this map.
      Specified by:
      put in interface Map<K,V>
      Parameters:
      oKey - key with which the specified value is to be associated
      oValue - value to be associated with the specified key
      Returns:
      previous value associated with specified key, or null if there was no mapping for key

    • putAll

      public void putAll(Map<? extends K,? extends V> map)
      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 in the passed map. The behavior of this operation is unspecified if the passed map is modified while the operation is in progress.
      Specified by:
      putAll in interface Map<K,V>
      Parameters:
      map - the Map containing the key/value pairings to put into this Map

    • remove

      public V remove(Object oKey)
      Removes the mapping for this key from this map if present. Expensive: updates both the underlying cache and the local cache.
      Specified by:
      remove in interface Map<K,V>
      Parameters:
      oKey - key whose mapping is to be removed from the map
      Returns:
      previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values.

    • size

      public int size()
      Returns the number of key-value mappings in this map.
      Specified by:
      size in interface Map<K,V>
      Returns:
      the number of key-value mappings in this map

    • values

      public Collection<V> values()
      Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It is not expected to support the add or addAll operations.
      Specified by:
      values in interface Map<K,V>
      Returns:
      a Collection view of the values contained in this map

    • getAll

      public Map<K,V> getAll(Collection<? extends K> colKeys)
      Get all the specified keys, if they are in the Map. For each key that is in the cache, that key and its corresponding value will be placed in the map that is returned by this method. The absence of a key in the returned map indicates that it was not in the cache, which may imply (for caches that can load behind the scenes) that the requested data could not be loaded.
      Parameters:
      colKeys - a collection of keys that may be in the named cache
      Returns:
      a Map of keys to values for the specified keys passed in colKeys

    • iterateKeys

      protected abstract Iterator<K> iterateKeys()
      Create an iterator over the keys in this Map. The Iterator must support remove() if the Map supports removal.
      Returns:
      a new instance of an Iterator over the keys in this Map

    • removeBlind

      protected boolean removeBlind(Object oKey)
      Removes the mapping for this key from this map if present. This method exists to allow sub-classes to optimize remove functionality for situations in which the original value is not required.
      Parameters:
      oKey - key whose mapping is to be removed from the map
      Returns:
      true iff the Map changed as the result of this operation

    • equals

      public boolean equals(Object o)
      Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps t1 and t2 represent the same mappings if t1.keySet().equals(t2.keySet()) and for every key k in t1.keySet(), (t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k))) . This ensures that the equals method works properly across different implementations of the map interface.
      Specified by:
      equals in interface Map<K,V>
      Overrides:
      equals in class Object
      Parameters:
      o - object to be compared for equality with this Map
      Returns:
      true if the specified object is equal to this Map

    • hashCode

      public int hashCode()
      Returns the hash code value for this Map. The hash code of a Map is defined to be the sum of the hash codes of each entry in the Map's entrySet() view. This ensures that t1.equals(t2) implies that t1.hashCode()==t2.hashCode() for any two maps t1 and t2, as required by the general contract of Object.hashCode.
      Specified by:
      hashCode in interface Map<K,V>
      Overrides:
      hashCode in class Object
      Returns:
      the hash code value for this Map

    • toString

      public String toString()
      Returns a string representation of this Map. The string representation consists of a list of key-value mappings in the order returned by the Map's entrySet view's iterator, enclosed in braces ("{}"). Adjacent mappings are separated by the characters ", " (comma and space). Each key-value mapping is rendered as the key followed by an equals sign ("=") followed by the associated value. Keys and values are converted to strings as by String.valueOf(Object).
      Overrides:
      toString in class Object
      Returns:
      a String representation of this Map

    • clone

      protected Object clone() throws CloneNotSupportedException
      Returns a shallow copy of this AbstractKeyBasedMap instance; the keySet, entrySet and values collections are not cloned or copied to (shared by) the clone.
      Overrides:
      clone in class Object
      Returns:
      a shallow copy of this map
      Throws:
      CloneNotSupportedException

    • instantiateKeySet

      protected Set<K> instantiateKeySet()
      Factory pattern: Create a Set that represents the keys in the Map
      Returns:
      a new instance of Set that represents the keys in the Map

    • instantiateEntrySet

      protected Set<Map.Entry<K,V>> instantiateEntrySet()
      Factory pattern: Create a Set that represents the entries in the Map.
      Returns:
      a new instance of Set that represents the entries in the Map

    • instantiateValues

      protected Collection<V> instantiateValues()
      Factory pattern: Instantiate the values Collection.
      Returns:
      a new instance of Collection that represents this Map's values