Module xyz.cofe.ecolls
Package xyz.cofe.collection

Class ClassMap<T>

java.lang.Object
xyz.cofe.collection.ClassMap<T>
All Implemented Interfaces:
java.util.Map<java.lang.Class,​T>, GetReadLock, GetWriteLock, ReadWriteLockProperty, ReadWriteLockSupport
public class ClassMap<T>
extends java.lang.Object
implements java.util.Map<java.lang.Class,​T>, ReadWriteLockProperty, ReadWriteLockSupport
Карта с возможностью поиска совместимых подтипов. 
 class A {}
 class B extends A {}
 ...
 cm = new ClassMap<Integer>
 cm.put( A.class, 1 )

 cm.fetch( A.class ) // вернет 1
 cm.fetch( B.class ) // вернет 1,
                     // т.к. B является подклассом A
Author:
nt.gocha@gmail.com

  • Nested Class Summary

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

    java.util.Map.Entry<K extends java.lang.Object,​V extends java.lang.Object>

  • Field Summary

    Fields 
    Modifier and Type Field Description
    protected java.util.Map<java.lang.Class,​T> map  
    protected ClassSet types  

  • Constructor Summary

    Constructors 
    Constructor Description
    ClassMap()
    Конструктор

  • Method Summary

    Modifier and Type Method Description
    void clear()
    Очищает карту от всех пар ключ/значение
    T compute​(java.lang.Class key, java.util.function.BiFunction<? super java.lang.Class,​? super T,​? extends T> remappingFunction)
    Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).
    T computeIfAbsent​(java.lang.Class key, java.util.function.Function<? super java.lang.Class,​? extends T> 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.
    T computeIfPresent​(java.lang.Class key, java.util.function.BiFunction<? super java.lang.Class,​? super T,​? extends T> 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​(java.lang.Object key)
    Проверяет наличие узла в ключа
    boolean containsValue​(java.lang.Object value)
    Проверяет наличие значения в карте
    java.util.Set<java.util.Map.Entry<java.lang.Class,​T>> entrySet()
    Возвращает множество пар
    T fetch​(java.lang.Class cls)
    Возвращает ассоциированное значение для ближайшего ковариантного типа
    void forEach​(java.util.function.BiConsumer<? super java.lang.Class,​? super T> action)
    Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
    T get​(java.lang.Class key)
    Возвращает по ключю значение
    T get​(java.lang.Object key)
    Возвращает по ключю значение
    T getOrDefault​(java.lang.Object key, T defaultValue)
    Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key.
    java.util.concurrent.locks.Lock getReadLock()
    Возвращает блокировку чтения
    java.util.concurrent.locks.Lock getWriteLock()
    Возвращает блокировку записи
    boolean isEmpty()
    Проверяет что карта пустая
    java.util.Set<java.lang.Class> keySet()
    Возвращает множество ключей
    T merge​(java.lang.Class key, T value, java.util.function.BiFunction<? super T,​? super T,​? extends T> 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.
    T put​(java.lang.Class key, T value)
    Указывает значение для ключа
    void putAll​(java.util.Map<? extends java.lang.Class,​? extends T> m)
    Добавляет карту в карту
    T putIfAbsent​(java.lang.Class key, T value)
    If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value.
    T remove​(java.lang.Class key)
    Удаляет пару для указанного ключа
    T remove​(java.lang.Object key)
    Удаляет пару для указанного ключа
    boolean remove​(java.lang.Object key, java.lang.Object value)
    Removes the entry for the specified key only if it is currently mapped to the specified value.
    T replace​(java.lang.Class key, T value)
    Replaces the entry for the specified key only if it is currently mapped to some value.
    boolean replace​(java.lang.Class key, T oldValue, T newValue)
    Replaces the entry for the specified key only if currently mapped to the specified value.
    void replaceAll​(java.util.function.BiFunction<? super java.lang.Class,​? super T,​? extends T> 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.
    int size()
    Возвращает кол-во пар значений в карте
    java.util.Collection<T> values()
    Возвращает значения

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface java.util.Map

    equals, hashCode

    Methods inherited from interface xyz.cofe.ecolls.ReadWriteLockProperty

    getReadWriteLock, setReadWriteLock

    Methods inherited from interface xyz.cofe.ecolls.ReadWriteLockSupport

    readLock, readLock, writeLock, writeLock

  • Field Details

    • map

      protected final java.util.Map<java.lang.Class,​T> map

    • types

      protected final ClassSet types

  • Constructor Details

    • ClassMap

      public ClassMap()
      Конструктор

  • Method Details

    • getReadLock

      public java.util.concurrent.locks.Lock getReadLock()
      Description copied from interface: GetReadLock
      Возвращает блокировку чтения
      Specified by:
      getReadLock in interface GetReadLock
      Specified by:
      getReadLock in interface ReadWriteLockProperty
      Specified by:
      getReadLock in interface ReadWriteLockSupport
      Returns:
      блокировка чтения

    • getWriteLock

      public java.util.concurrent.locks.Lock getWriteLock()
      Description copied from interface: GetWriteLock
      Возвращает блокировку записи
      Specified by:
      getWriteLock in interface GetWriteLock
      Specified by:
      getWriteLock in interface ReadWriteLockProperty
      Specified by:
      getWriteLock in interface ReadWriteLockSupport
      Returns:
      блокировка записи

    • put

      public T put​(java.lang.Class key, T value)
      Указывает значение для ключа
      Specified by:
      put in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - ключ
      value - значение
      Returns:
      предыдущее значение

    • size

      public int size()
      Возвращает кол-во пар значений в карте
      Specified by:
      size in interface java.util.Map<java.lang.Class,​T>
      Returns:
      кол-во пар значений

    • isEmpty

      public boolean isEmpty()
      Проверяет что карта пустая
      Specified by:
      isEmpty in interface java.util.Map<java.lang.Class,​T>
      Returns:
      true - карта пустая

    • get

      public T get​(java.lang.Class key)
      Возвращает по ключю значение
      Parameters:
      key - ключ
      Returns:
      значение

    • remove

      public T remove​(java.lang.Class key)
      Удаляет пару для указанного ключа
      Parameters:
      key - ключ
      Returns:
      удаленное значение

    • putAll

      public void putAll​(java.util.Map<? extends java.lang.Class,​? extends T> m)
      Добавляет карту в карту
      Specified by:
      putAll in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      m - карта

    • keySet

      public java.util.Set<java.lang.Class> keySet()
      Возвращает множество ключей
      Specified by:
      keySet in interface java.util.Map<java.lang.Class,​T>
      Returns:
      множество ключей

    • values

      public java.util.Collection<T> values()
      Возвращает значения
      Specified by:
      values in interface java.util.Map<java.lang.Class,​T>
      Returns:
      значения

    • entrySet

      public java.util.Set<java.util.Map.Entry<java.lang.Class,​T>> entrySet()
      Возвращает множество пар
      Specified by:
      entrySet in interface java.util.Map<java.lang.Class,​T>
      Returns:
      множество пар

    • fetch

      public T fetch​(java.lang.Class cls)
      Возвращает ассоциированное значение для ближайшего ковариантного типа
      Parameters:
      cls - ковариантного тип
      Returns:
      ассоциац значение или null

    • containsKey

      public boolean containsKey​(java.lang.Object key)
      Проверяет наличие узла в ключа
      Specified by:
      containsKey in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - ключ
      Returns:
      true - ключ присуствует

    • containsValue

      public boolean containsValue​(java.lang.Object value)
      Проверяет наличие значения в карте
      Specified by:
      containsValue in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      value - значение
      Returns:
      true - значение присуствует

    • get

      public T get​(java.lang.Object key)
      Возвращает по ключю значение
      Specified by:
      get in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - ключ
      Returns:
      значение

    • remove

      public T remove​(java.lang.Object key)
      Удаляет пару для указанного ключа
      Specified by:
      remove in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - ключ
      Returns:
      удаленное значение

    • clear

      public void clear()
      Очищает карту от всех пар ключ/значение
      Specified by:
      clear in interface java.util.Map<java.lang.Class,​T>

    • getOrDefault

      public T getOrDefault​(java.lang.Object key, T defaultValue)
      Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key. The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.
      Specified by:
      getOrDefault in interface java.util.Map<java.lang.Class,​T>
      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
      Throws:
      java.lang.ClassCastException - if the key is of an inappropriate type for this map (optional)
      java.lang.NullPointerException - if the specified key is null and this map does not permit null keys (optional)
      Since:
      1.8

    • forEach

      public void forEach​(java.util.function.BiConsumer<? super java.lang.Class,​? super T> action)
      Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller. The default implementation is equivalent to, for this map: 
       
 for (Map.Entry<K, V> entry : map.entrySet())
     action.accept(entry.getKey(), entry.getValue());
      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.
      Specified by:
      forEach in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      action - The action to be performed for each entry
      Throws:
      java.lang.NullPointerException - if the specified action is null
      java.util.ConcurrentModificationException - if an entry is found to be removed during iteration
      Since:
      1.8

    • replaceAll

      public void replaceAll​(java.util.function.BiFunction<? super java.lang.Class,​? super T,​? extends T> 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.

      The default implementation is equivalent to, for this map: 

       
 for (Map.Entry<K, V> entry : map.entrySet())
     entry.setValue(function.apply(entry.getKey(), entry.getValue()));

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.

      Specified by:
      replaceAll in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      function - the function to apply to each entry
      Throws:
      java.lang.UnsupportedOperationException - if the set operation is not supported by this map's entry set iterator.
      java.lang.ClassCastException - if the class of a replacement value prevents it from being stored in this map
      java.lang.NullPointerException - if the specified function is null, or the specified replacement value is null, and this map does not permit null values
      java.lang.ClassCastException - if a replacement value is of an inappropriate type for this map (optional)
      java.lang.NullPointerException - if function or a replacement value is null, and this map does not permit null keys or values (optional)
      java.lang.IllegalArgumentException - if some property of a replacement value prevents it from being stored in this map (optional)
      java.util.ConcurrentModificationException - if an entry is found to be removed during iteration
      Since:
      1.8

    • putIfAbsent

      public T putIfAbsent​(java.lang.Class key, T value)
      If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value. The default implementation is equivalent to, for this map: 
       
 V v = map.get(key);
 if (v == null)
     v = map.put(key, value);

 return v;

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.

      Specified by:
      putIfAbsent in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - key with which the specified value is to be associated
      value - value to be associated with the specified key
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the key, if the implementation supports null values.)
      Throws:
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the key or value is of an inappropriate type for this map (optional)
      java.lang.NullPointerException - if the specified key or value is null, and this map does not permit null keys or values (optional)
      java.lang.IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)
      Since:
      1.8

    • remove

      public boolean remove​(java.lang.Object key, java.lang.Object value)
      Removes the entry for the specified key only if it is currently mapped to the specified value. The default implementation is equivalent to, for this map: 
       
 if (map.containsKey(key) && Objects.equals(map.get(key), value)) {
     map.remove(key);
     return true;
 } else
     return false;

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.

      Specified by:
      remove in interface java.util.Map<java.lang.Class,​T>
      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
      Throws:
      java.lang.UnsupportedOperationException - if the remove operation is not supported by this map (optional)
      java.lang.ClassCastException - if the key or value is of an inappropriate type for this map (optional)
      java.lang.NullPointerException - if the specified key or value is null, and this map does not permit null keys or values (optional)
      Since:
      1.8

    • replace

      public boolean replace​(java.lang.Class key, T oldValue, T newValue)
      Replaces the entry for the specified key only if currently mapped to the specified value. The default implementation is equivalent to, for this map: 
       
 if (map.containsKey(key) && Objects.equals(map.get(key), value)) {
     map.put(key, newValue);
     return true;
 } else
     return false;
      The default implementation does not throw NullPointerException for maps that do not support null values if oldValue is null unless newValue is also null.

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.

      Specified by:
      replace in interface java.util.Map<java.lang.Class,​T>
      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
      Throws:
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the class of a specified key or value prevents it from being stored in this map
      java.lang.NullPointerException - if a specified key or newValue is null, and this map does not permit null keys or values
      java.lang.NullPointerException - if oldValue is null and this map does not permit null values (optional)
      java.lang.IllegalArgumentException - if some property of a specified key or value prevents it from being stored in this map
      Since:
      1.8

    • replace

      public T replace​(java.lang.Class key, T value)
      Replaces the entry for the specified key only if it is currently mapped to some value. The default implementation is equivalent to, for this map: 
       
 if (map.containsKey(key)) {
     return map.put(key, value);
 } else
     return null;

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties.

      Specified by:
      replace in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - key with which the specified value is associated
      value - value to be associated with the specified key
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the key, if the implementation supports null values.)
      Throws:
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)
      java.lang.NullPointerException - if the specified key or value is null, and this map does not permit null keys or values
      java.lang.IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map
      Since:
      1.8

    • computeIfAbsent

      public T computeIfAbsent​(java.lang.Class key, java.util.function.Function<? super java.lang.Class,​? extends T> 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 mapping function returns null, no mapping is recorded. If the mapping function itself throws an (unchecked) exception, the exception is rethrown, and no mapping is recorded. The most common usage is to construct a new object serving as an initial mapped value or memoized result, as in: 

       
 map.computeIfAbsent(key, k -> new Value(f(k)));

      Or to implement a multi-value map, Map<K,Collection<V>>, supporting multiple values per key: 

       
 map.computeIfAbsent(key, k -> new HashSet<V>()).add(v);

      The mapping function should not modify this map during computation. The default implementation is equivalent to the following steps for this map, then returning the current value or null if now absent: 

       
 if (map.get(key) == null) {
     V newValue = mappingFunction.apply(key);
     if (newValue != null)
         map.put(key, newValue);
 }

      The default implementation makes no guarantees about detecting if the mapping function modifies this map during computation and, if appropriate, reporting an error. Non-concurrent implementations should override this method and, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the mapping function modifies this map during computation. Concurrent implementations should override this method and, on a best-effort basis, throw an IllegalStateException if it is detected that the mapping function modifies this map during computation and as a result computation would never complete.

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties. In particular, all implementations of subinterface ConcurrentMap must document whether the mapping function is applied once atomically only if the value is not present.

      Specified by:
      computeIfAbsent in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - key with which the specified value is to be associated
      mappingFunction - the mapping 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
      Throws:
      java.lang.NullPointerException - if the specified key is null and this map does not support null keys, or the mappingFunction is null
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)
      java.lang.IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)
      Since:
      1.8

    • computeIfPresent

      public T computeIfPresent​(java.lang.Class key, java.util.function.BiFunction<? super java.lang.Class,​? super T,​? extends T> 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 remapping function returns null, the mapping is removed. If the remapping function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

      The remapping function should not modify this map during computation. The default implementation is equivalent to performing the following steps for this map, then returning the current value or null if now absent: 

       
 if (map.get(key) != null) {
     V oldValue = map.get(key);
     V newValue = remappingFunction.apply(key, oldValue);
     if (newValue != null)
         map.put(key, newValue);
     else
         map.remove(key);
 }

      The default implementation makes no guarantees about detecting if the remapping function modifies this map during computation and, if appropriate, reporting an error. Non-concurrent implementations should override this method and, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the remapping function modifies this map during computation. Concurrent implementations should override this method and, on a best-effort basis, throw an IllegalStateException if it is detected that the remapping function modifies this map during computation and as a result computation would never complete.

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties. In particular, all implementations of subinterface ConcurrentMap must document whether the remapping function is applied once atomically only if the value is not present.

      Specified by:
      computeIfPresent in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - key with which the specified value is to be associated
      remappingFunction - the remapping function to compute a value
      Returns:
      the new value associated with the specified key, or null if none
      Throws:
      java.lang.NullPointerException - if the specified key is null and this map does not support null keys, or the remappingFunction is null
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)
      java.lang.IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)
      Since:
      1.8

    • compute

      public T compute​(java.lang.Class key, java.util.function.BiFunction<? super java.lang.Class,​? super T,​? extends T> remappingFunction)
      Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). For example, to either create or append a String msg to a value mapping: 
       
 map.compute(key, (k, v) -> (v == null) ? msg : v.concat(msg))
      (Method merge() is often simpler to use for such purposes.)

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

      The remapping function should not modify this map during computation. The default implementation is equivalent to performing the following steps for this map, then returning the current value or null if absent: 

       
 V oldValue = map.get(key);
 V newValue = remappingFunction.apply(key, oldValue);
 if (oldValue != null) {
    if (newValue != null)
       map.put(key, newValue);
    else
       map.remove(key);
 } else {
    if (newValue != null)
       map.put(key, newValue);
    else
       return null;
 }

      The default implementation makes no guarantees about detecting if the remapping function modifies this map during computation and, if appropriate, reporting an error. Non-concurrent implementations should override this method and, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the remapping function modifies this map during computation. Concurrent implementations should override this method and, on a best-effort basis, throw an IllegalStateException if it is detected that the remapping function modifies this map during computation and as a result computation would never complete.

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties. In particular, all implementations of subinterface ConcurrentMap must document whether the remapping function is applied once atomically only if the value is not present.

      Specified by:
      compute in interface java.util.Map<java.lang.Class,​T>
      Parameters:
      key - key with which the specified value is to be associated
      remappingFunction - the remapping function to compute a value
      Returns:
      the new value associated with the specified key, or null if none
      Throws:
      java.lang.NullPointerException - if the specified key is null and this map does not support null keys, or the remappingFunction is null
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)
      java.lang.IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)
      Since:
      1.8

    • merge

      public T merge​(java.lang.Class key, T value, java.util.function.BiFunction<? super T,​? super T,​? extends T> 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. For example, to either create or append a String msg to a value mapping: 
       
 map.merge(key, msg, String::concat)

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

      The remapping function should not modify this map during computation. The default implementation is equivalent to performing the following steps for this map, then returning the current value or null if absent: 

       
 V oldValue = map.get(key);
 V newValue = (oldValue == null) ? value :
              remappingFunction.apply(oldValue, value);
 if (newValue == null)
     map.remove(key);
 else
     map.put(key, newValue);

      The default implementation makes no guarantees about detecting if the remapping function modifies this map during computation and, if appropriate, reporting an error. Non-concurrent implementations should override this method and, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the remapping function modifies this map during computation. Concurrent implementations should override this method and, on a best-effort basis, throw an IllegalStateException if it is detected that the remapping function modifies this map during computation and as a result computation would never complete.

      The default implementation makes no guarantees about synchronization or atomicity properties of this method. Any implementation providing atomicity guarantees must override this method and document its concurrency properties. In particular, all implementations of subinterface ConcurrentMap must document whether the remapping function is applied once atomically only if the value is not present.

      Specified by:
      merge in interface java.util.Map<java.lang.Class,​T>
      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 remapping 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
      Throws:
      java.lang.UnsupportedOperationException - if the put operation is not supported by this map (optional)
      java.lang.ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)
      java.lang.IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)
      java.lang.NullPointerException - if the specified key is null and this map does not support null keys or the value or remappingFunction is null
      Since:
      1.8