Nested Class Summary

Method Summary

Method Details

• size

  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.

  Returns:

  the number of key-value mappings in this map

• isEmpty

  boolean isEmpty()

  Returns true if this map contains no key-value mappings.

  Returns:

  true if this map contains no key-value mappings

• containsKey

  boolean containsKey(Object key)

  Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that Objects.equals(key, k). (There can be at most one such mapping.)

  Parameters:

  key - key whose presence in this map is to be tested

  Returns:

  true if this map contains a mapping for the specified key

  Throws:

  ClassCastException - if the key is of an inappropriate type for this map (optional)

  NullPointerException - if the specified key is null and this map does not permit null keys (optional)

• containsValue

  boolean containsValue(Object value)

  Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that Objects.equals(value, v). This operation will probably require time linear in the map size for most implementations of the Map interface.

  Parameters:

  value - value whose presence in this map is to be tested

  Returns:

  true if this map maps one or more keys to the specified value

  Throws:

  ClassCastException - if the value is of an inappropriate type for this map (optional)

  NullPointerException - if the specified value is null and this map does not permit null values (optional)

• get

  V get(Object key)

  Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

  More formally, if this map contains a mapping from a key k to a value v such that Objects.equals(key, k), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

  If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

  Parameters:

  key - the key whose associated value is to be returned

  Returns:

  the value to which the specified key is mapped, or null if this map contains no mapping for the key

  Throws:

  ClassCastException - if the key is of an inappropriate type for this map (optional)

  NullPointerException - if the specified key is null and this map does not permit null keys (optional)

• put

  V put(K key, V value)

  Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)

  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 key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)

  Throws:

  UnsupportedOperationException - if the put operation is not supported by this map

  ClassCastException - if the class of the specified key or value prevents it from being stored in this map

  NullPointerException - if the specified key or value is null and this map does not permit null keys or values

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map

• remove

  V remove(Object key)

  Removes the mapping for a key from this map if it is present (optional operation). More formally, if this map contains a mapping from key k to value v such that Objects.equals(key, k), that mapping is removed. (The map can contain at most one such mapping.)

  Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.

  If this map permits null values, then a return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.

  The map will not contain a mapping for the specified key once the call returns.

  Parameters:

  key - key whose mapping is to be removed from the map

  Returns:

  the previous value associated with key, or null if there was no mapping for key.

  Throws:

  UnsupportedOperationException - if the remove operation is not supported by this map

  ClassCastException - if the key is of an inappropriate type for this map (optional)

  NullPointerException - if the specified key is null and this map does not permit null keys (optional)

• putAll

  void putAll(Map<? extends K, ? extends V> m)

  Copies all of the mappings from the specified map to this map (optional operation). 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. If the specified map has a defined encounter order, processing of its mappings generally occurs in that order.

  Parameters:

  m - mappings to be stored in this map

  Throws:

  UnsupportedOperationException - if the putAll operation is not supported by this map

  ClassCastException - if the class of a key or value in the specified map prevents it from being stored in this map

  NullPointerException - if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values

  IllegalArgumentException - if some property of a key or value in the specified map prevents it from being stored in this map

• clear

  void clear()

  Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.

  Throws:

  UnsupportedOperationException - if the clear operation is not supported by this map

• keySet

  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 does not support the add or addAll operations.

  Returns:

  a set view of the keys contained in this map

• values

  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 does not support the add or addAll operations.

  Returns:

  a collection view of the values contained in this map

• entrySet

  Set<Map.Entry<K,V>> entrySet()

  Returns a Set view of the mappings 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, or through 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 does not support the add or addAll operations.

  Returns:

  a set view of the mappings contained in this map

• equals

  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 m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). This ensures that the equals method works properly across different implementations of the Map interface.

  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

  See Also:

  • Object.hashCode()
  • HashMap

• hashCode

  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 m1.equals(m2) implies that m1.hashCode()==m2.hashCode() for any two maps m1 and m2, as required by the general contract of Object.hashCode().

  Overrides:

  hashCode in class Object

  Returns:

  the hash code value for this map

  See Also:

  • Map.Entry.hashCode()
  • Object.equals(Object)
  • equals(Object)

• getOrDefault

  default 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.

  Implementation Requirements:

  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.

  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:

  ClassCastException - if the key is of an inappropriate type for this map (optional)

  NullPointerException - if the specified key is null and this map does not permit null keys (optional)

  Since:

  1.8

• forEach

  default void forEach(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. 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.

  Implementation Requirements:

  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.

  Parameters:

  action - The action to be performed for each entry

  Throws:

  NullPointerException - if the specified action is null

  ConcurrentModificationException - if an entry is found to be removed during iteration

  Since:

  1.8

• replaceAll

  default void replaceAll(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 (optional operation). Exceptions thrown by the function are relayed to the caller.

  Implementation Requirements:

  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.

  Parameters:

  function - the function to apply to each entry

  Throws:

  UnsupportedOperationException - if the replaceAll operation is not supported by this map (optional)

  ClassCastException - if the class of a replacement value prevents it from being stored in this map (optional)

  NullPointerException - if the specified function is null, or if a replacement value is null and this map does not permit null values (optional)

  IllegalArgumentException - if some property of a replacement value prevents it from being stored in this map (optional)

  ConcurrentModificationException - if an entry is found to be removed during iteration

  Since:

  1.8

• putIfAbsent

  default V putIfAbsent(K key, V 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 (optional operation).

  Implementation Requirements:

  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.

  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:

  UnsupportedOperationException - if the putIfAbsent operation is not supported by this map (optional)

  ClassCastException - if the key or value is of an inappropriate type for this map (optional)

  NullPointerException - if the specified key or value is null, and this map does not permit null keys or values (optional)

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)

  Since:

  1.8

• remove

  default boolean remove(Object key, Object value)

  Removes the entry for the specified key only if it is currently mapped to the specified value (optional operation).

  Implementation Requirements:

  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.

  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:

  UnsupportedOperationException - if the remove operation is not supported by this map (optional)

  ClassCastException - if the key or value is of an inappropriate type for this map (optional)

  NullPointerException - if the specified key or value is null, and this map does not permit null keys or values (optional)

  Since:

  1.8

• replace

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

  Replaces the entry for the specified key only if currently mapped to the specified value (optional operation).

  Implementation Requirements:

  The default implementation is equivalent to, for this map:

   
   if (map.containsKey(key) && Objects.equals(map.get(key), oldValue)) {
       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.

  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:

  UnsupportedOperationException - if the replace operation is not supported by this map (optional)

  ClassCastException - if the class of a specified key or value prevents it from being stored in this map

  NullPointerException - if a specified key or newValue is null, and this map does not permit null keys or values

  NullPointerException - if oldValue is null and this map does not permit null values (optional)

  IllegalArgumentException - if some property of a specified key or value prevents it from being stored in this map

  Since:

  1.8

• replace

  default V replace(K key, V value)

  Replaces the entry for the specified key only if it is currently mapped to some value (optional operation).

  Implementation Requirements:

  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.

  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:

  UnsupportedOperationException - if the replace operation is not supported by this map (optional)

  ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)

  NullPointerException - if the specified key or value is null, and this map does not permit null keys or values

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map

  Since:

  1.8

• computeIfAbsent

  default V computeIfAbsent(K key, 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 (optional operation).

  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.

  Implementation Requirements:

  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.

  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:

  NullPointerException - if the specified key is null and this map does not support null keys, or the mappingFunction is null

  UnsupportedOperationException - if the computeIfAbsent operation is not supported by this map (optional)

  ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)

  Since:

  1.8

• computeIfPresent

  default V computeIfPresent(K key, 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 (optional operation).

  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.

  Implementation Requirements:

  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.

  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:

  NullPointerException - if the specified key is null and this map does not support null keys, or the remappingFunction is null

  UnsupportedOperationException - if the computeIfPresent operation is not supported by this map (optional)

  ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)

  Since:

  1.8

• compute

  default V compute(K key, 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 (optional operation). 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.

  Implementation Requirements:

  The default implementation is equivalent to performing the following steps for this map:

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

  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:

  NullPointerException - if the specified key is null and this map does not support null keys, or the remappingFunction is null

  UnsupportedOperationException - if the compute operation is not supported by this map (optional)

  ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)

  Since:

  1.8

• merge

  default V merge(K key, V value, 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 (optional operation). 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.

  Implementation Requirements:

  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.

  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:

  UnsupportedOperationException - if the merge operation is not supported by this map (optional)

  ClassCastException - if the class of the specified key or value prevents it from being stored in this map (optional)

  IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map (optional)

  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

• of

  static <K,V> Map<K,V> of()

  Returns an unmodifiable map containing zero mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Returns:

  an empty Map

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1)

  Returns an unmodifiable map containing a single mapping. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the mapping's key

  v1 - the mapping's value

  Returns:

  a Map containing the specified mapping

  Throws:

  NullPointerException - if the key or the value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2)

  Returns an unmodifiable map containing two mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if the keys are duplicates

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3)

  Returns an unmodifiable map containing three mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4)

  Returns an unmodifiable map containing four mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5)

  Returns an unmodifiable map containing five mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  k5 - the fifth mapping's key

  v5 - the fifth mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6)

  Returns an unmodifiable map containing six mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  k5 - the fifth mapping's key

  v5 - the fifth mapping's value

  k6 - the sixth mapping's key

  v6 - the sixth mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7)

  Returns an unmodifiable map containing seven mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  k5 - the fifth mapping's key

  v5 - the fifth mapping's value

  k6 - the sixth mapping's key

  v6 - the sixth mapping's value

  k7 - the seventh mapping's key

  v7 - the seventh mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7, K k8, V v8)

  Returns an unmodifiable map containing eight mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  k5 - the fifth mapping's key

  v5 - the fifth mapping's value

  k6 - the sixth mapping's key

  v6 - the sixth mapping's value

  k7 - the seventh mapping's key

  v7 - the seventh mapping's value

  k8 - the eighth mapping's key

  v8 - the eighth mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7, K k8, V v8, K k9, V v9)

  Returns an unmodifiable map containing nine mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  k5 - the fifth mapping's key

  v5 - the fifth mapping's value

  k6 - the sixth mapping's key

  v6 - the sixth mapping's value

  k7 - the seventh mapping's key

  v7 - the seventh mapping's value

  k8 - the eighth mapping's key

  v8 - the eighth mapping's value

  k9 - the ninth mapping's key

  v9 - the ninth mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• of

  static <K,V> Map<K,V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7, K k8, V v8, K k9, V v9, K k10, V v10)

  Returns an unmodifiable map containing ten mappings. See Unmodifiable Maps for details.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  k1 - the first mapping's key

  v1 - the first mapping's value

  k2 - the second mapping's key

  v2 - the second mapping's value

  k3 - the third mapping's key

  v3 - the third mapping's value

  k4 - the fourth mapping's key

  v4 - the fourth mapping's value

  k5 - the fifth mapping's key

  v5 - the fifth mapping's value

  k6 - the sixth mapping's key

  v6 - the sixth mapping's value

  k7 - the seventh mapping's key

  v7 - the seventh mapping's value

  k8 - the eighth mapping's key

  v8 - the eighth mapping's value

  k9 - the ninth mapping's key

  v9 - the ninth mapping's value

  k10 - the tenth mapping's key

  v10 - the tenth mapping's value

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any key or value is null

  Since:

  9

• ofEntries

  @SafeVarargs static <K,V> Map<K,V> ofEntries(Map.Entry<? extends K, ? extends V>... entries)

  Returns an unmodifiable map containing keys and values extracted from the given entries. The entries themselves are not stored in the map. See Unmodifiable Maps for details.

  API Note:

  It is convenient to create the map entries using the Map.entry() method. For example,

  
       import static java.util.Map.entry;
  
       Map<Integer,String> map = Map.ofEntries(
           entry(1, "a"),
           entry(2, "b"),
           entry(3, "c"),
           ...
           entry(26, "z"));
   

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  entries - Map.Entrys containing the keys and values from which the map is populated

  Returns:

  a Map containing the specified mappings

  Throws:

  IllegalArgumentException - if there are any duplicate keys

  NullPointerException - if any entry, key, or value is null, or if the entries array is null

  Since:

  9

  See Also:

  • Map.entry()

• entry

  static <K,V> Map.Entry<K,V> entry(K k, V v)

  Returns an unmodifiable Map.Entry containing the given key and value. These entries are suitable for populating Map instances using the Map.ofEntries() method. The Entry instances created by this method have the following characteristics:

  • They disallow null keys and values. Attempts to create them using a null key or value result in NullPointerException.
  • They are unmodifiable. Calls to Entry.setValue() on a returned Entry result in UnsupportedOperationException.
  • They are not serializable.
  • They are value-based. Programmers should treat instances that are equal as interchangeable and should not use them for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail. Callers should make no assumptions about the identity of the returned instances. This method is free to create new instances or reuse existing ones.

  API Note:

  For a serializable Entry, see AbstractMap.SimpleEntry or AbstractMap.SimpleImmutableEntry.

  Type Parameters:

  K - the key's type

  V - the value's type

  Parameters:

  k - the key

  v - the value

  Returns:

  an Entry containing the specified key and value

  Throws:

  NullPointerException - if the key or value is null

  Since:

  9

  See Also:

  • Map.ofEntries()

• copyOf

  static <K,V> Map<K,V> copyOf(Map<? extends K, ? extends V> map)

  Returns an unmodifiable Map containing the entries of the given Map. The given Map must not be null, and it must not contain any null keys or values. If the given Map is subsequently modified, the returned Map will not reflect such modifications.

  Implementation Note:

  If the given Map is an unmodifiable Map, calling copyOf will generally not create a copy.

  Type Parameters:

  K - the Map's key type

  V - the Map's value type

  Parameters:

  map - a Map from which entries are drawn, must be non-null

  Returns:

  a Map containing the entries of the given Map

  Throws:

  NullPointerException - if map is null, or if it contains any null keys or values

  Since:

  10