Class KeyComparatorHashMap<K,​V>

  • Type Parameters:
    K - Type of keys
    V - Type of values
    All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, java.util.Map<K,​V>
    Direct Known Subclasses:
    KeyComparatorLinkedHashMap

    public class KeyComparatorHashMap<K,​V>
    extends java.util.AbstractMap<K,​V>
    implements java.util.Map<K,​V>, java.lang.Cloneable, java.io.Serializable
    A implementation similar to HashMap but supports the comparison of keys using a KeyComparator.
    See Also:
    Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      (package private) static int DEFAULT_INITIAL_CAPACITY
      The default initial capacity - MUST be a power of two.
      (package private) static float DEFAULT_LOAD_FACTOR
      The load factor used when none specified in constructor.
      private java.util.Set<java.util.Map.Entry<K,​V>> entrySet  
      (package private) KeyComparator<K> keyComparator  
      (package private) float loadFactor
      The load factor for the hash table.
      (package private) static int MAXIMUM_CAPACITY
      The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments.
      (package private) int modCount
      The number of times this HashMap has been structurally modified Structural modifications are those that change the number of mappings in the HashMap or otherwise modify its internal structure (e.g., rehash).
      (package private) static java.lang.Object NULL_KEY
      Value representing null keys inside tables.
      private static long serialVersionUID  
      (package private) int size
      The number of key-value mappings contained in this identity hash map.
      (package private) KeyComparatorHashMap.Entry<K,​V>[] table
      The table, resized as necessary.
      (package private) int threshold
      The next ss value at which to resize (capacity * load factor).
    • Constructor Summary

      Constructors 
      Constructor Description
      KeyComparatorHashMap​(int initialCapacity, float loadFactor, KeyComparator<K> keyComparator)
      Constructs an empty HashMap with the specified initial capacity and load factor.
      KeyComparatorHashMap​(int initialCapacity, KeyComparator<K> keyComparator)
      Constructs an empty HashMap with the specified initial capacity and the default load factor (0.75).
      KeyComparatorHashMap​(java.util.Map<? extends K,​? extends V> m, KeyComparator<K> keyComparator)
      Constructs a new HashMap with the same mappings as the specified Map.
      KeyComparatorHashMap​(KeyComparator<K> keyComparator)
      Constructs an empty HashMap with the default initial capacity (16) and the default load factor (0.75).
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      (package private) void addEntry​(int hash, K key, V value, int bucketIndex)
      Add a new entry with the specified key, value and hash code to the specified bucket.
      (package private) int capacity()  
      void clear()
      Removes all mappings from this map.
      java.lang.Object clone()
      Returns a shallow copy of this HashMap instance: the keys and values themselves are not cloned.
      boolean containsKey​(java.lang.Object key)
      Returns true if this map contains a mapping for the specified key.
      private boolean containsNullValue()
      Special-case code for containsValue with null argument
      boolean containsValue​(java.lang.Object value)
      Returns true if this map maps one or more keys to the specified value.
      (package private) void createEntry​(int hash, K key, V value, int bucketIndex)
      Like addEntry except that this version is used when creating entries as part of Map construction or "pseudo-construction" (cloning, deserialization).
      java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
      Returns a collection view of the mappings contained in this map.
      (package private) static boolean eq​(java.lang.Object x, java.lang.Object y)
      Check for equality of non-null reference x and possibly-null y.
      V get​(java.lang.Object key)
      Returns the value to which the specified key is mapped in this identity hash map, or null if the map contains no mapping for this key.
      (package private) KeyComparatorHashMap.Entry<K,​V> getEntry​(K key)
      Returns the entry associated with the specified key in the HashMap.
      int getModCount()
      Get the number of times this HashMap has been structurally modified Structural modifications are those that change the number of mappings in the HashMap or otherwise modify its internal structure (e.g., rehash).
      (package private) int hash​(int h)  
      (package private) static int hash​(java.lang.Object x)
      Returns a hash value for the specified object.
      (package private) static int indexFor​(int h, int length)
      Returns index for hash code h.
      (package private) void init()
      Initialization hook for subclasses.
      boolean isEmpty()
      Returns true if this map contains no key-value mappings.
      (package private) static <T> boolean isNull​(T key)  
      (package private) boolean keyComparatorEq​(K x, K y)
      Check for equality of non-null reference x and possibly-null y.
      (package private) int keyComparatorHash​(K k)  
      (package private) float loadFactor()  
      (package private) static <T> T maskNull​(T key)
      Returns internal representation for key.
      (package private) java.util.Iterator<java.util.Map.Entry<K,​V>> newEntryIterator()  
      (package private) java.util.Iterator<K> newKeyIterator()  
      (package private) java.util.Iterator<V> newValueIterator()  
      V put​(K key, V value)
      Associates the specified value with the specified key in this map.
      void putAll​(java.util.Map<? extends K,​? extends V> m)
      Copies all of the mappings from the specified map to this map These mappings will replace any mappings that this map had for any of the keys currently in the specified map.
      private void putAllForCreate​(java.util.Map<? extends K,​? extends V> m)  
      private void putForCreate​(K key, V value)
      This method is used instead of put by constructors and pseudoconstructors (clone, readObject).
      private void readObject​(java.io.ObjectInputStream s)
      Reconstitute the HashMap instance from a stream (i.e., deserialize it).
      V remove​(java.lang.Object key)
      Removes the mapping for this key from this map if present.
      (package private) KeyComparatorHashMap.Entry<K,​V> removeEntryForKey​(java.lang.Object key)
      Removes and returns the entry associated with the specified key in the HashMap.
      (package private) KeyComparatorHashMap.Entry<K,​V> removeMapping​(java.lang.Object o)
      Special version of remove for EntrySet.
      (package private) void resize​(int newCapacity)
      Rehashes the contents of this map into a new array with a larger capacity.
      int size()
      Returns the number of key-value mappings in this map.
      (package private) void transfer​(KeyComparatorHashMap.Entry<K,​V>[] newTable)
      Transfer all entries from current table to newTable.
      (package private) static <T> T unmaskNull​(T key)
      Returns key represented by specified internal representation.
      private void writeObject​(java.io.ObjectOutputStream s)
      Save the state of the HashMap instance to a stream (i.e., serialize it).
      • Methods inherited from class java.util.AbstractMap

        equals, hashCode, keySet, toString, values
      • Methods inherited from class java.lang.Object

        finalize, getClass, notify, notifyAll, wait, wait, wait
      • Methods inherited from interface java.util.Map

        compute, computeIfAbsent, computeIfPresent, equals, forEach, getOrDefault, hashCode, keySet, merge, putIfAbsent, remove, replace, replace, replaceAll, values
    • Field Detail

      • DEFAULT_INITIAL_CAPACITY

        static final int DEFAULT_INITIAL_CAPACITY
        The default initial capacity - MUST be a power of two.
        See Also:
        Constant Field Values
      • MAXIMUM_CAPACITY

        static final int MAXIMUM_CAPACITY
        The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments. MUST be a power of two <= 1<<30.
        See Also:
        Constant Field Values
      • DEFAULT_LOAD_FACTOR

        static final float DEFAULT_LOAD_FACTOR
        The load factor used when none specified in constructor.
        See Also:
        Constant Field Values
      • size

        transient int size
        The number of key-value mappings contained in this identity hash map.
      • threshold

        int threshold
        The next ss value at which to resize (capacity * load factor).
      • loadFactor

        final float loadFactor
        The load factor for the hash table.
      • modCount

        transient volatile int modCount
        The number of times this HashMap has been structurally modified Structural modifications are those that change the number of mappings in the HashMap or otherwise modify its internal structure (e.g., rehash). This field is used to make iterators on Collection-views of the HashMap fail-fast. (See ConcurrentModificationException).
      • NULL_KEY

        static final java.lang.Object NULL_KEY
        Value representing null keys inside tables.
      • entrySet

        private transient java.util.Set<java.util.Map.Entry<K,​V>> entrySet
    • Constructor Detail

      • KeyComparatorHashMap

        public KeyComparatorHashMap​(int initialCapacity,
                                    float loadFactor,
                                    KeyComparator<K> keyComparator)
        Constructs an empty HashMap with the specified initial capacity and load factor.
        Parameters:
        initialCapacity - The initial capacity.
        loadFactor - The load factor.
        keyComparator - the map key comparator.
        Throws:
        java.lang.IllegalArgumentException - if the initial capacity is negative or the load factor is nonpositive.
      • KeyComparatorHashMap

        public KeyComparatorHashMap​(int initialCapacity,
                                    KeyComparator<K> keyComparator)
        Constructs an empty HashMap with the specified initial capacity and the default load factor (0.75).
        Parameters:
        initialCapacity - the initial capacity.
        keyComparator - the map key comparator.
        Throws:
        java.lang.IllegalArgumentException - if the initial capacity is negative.
      • KeyComparatorHashMap

        public KeyComparatorHashMap​(KeyComparator<K> keyComparator)
        Constructs an empty HashMap with the default initial capacity (16) and the default load factor (0.75).
        Parameters:
        keyComparator - the map key comparator.
      • KeyComparatorHashMap

        public KeyComparatorHashMap​(java.util.Map<? extends K,​? extends V> m,
                                    KeyComparator<K> keyComparator)
        Constructs a new HashMap with the same mappings as the specified Map. The HashMap is created with default load factor (0.75) and an initial capacity sufficient to hold the mappings in the specified Map.
        Parameters:
        m - the map whose mappings are to be placed in this map.
        keyComparator - the comparator
        Throws:
        java.lang.NullPointerException - if the specified map is null.
    • Method Detail

      • getModCount

        public int getModCount()
        Get the number of times this HashMap has been structurally modified Structural modifications are those that change the number of mappings in the HashMap or otherwise modify its internal structure (e.g., rehash).
        Returns:
        return the modification count.
      • init

        void init()
        Initialization hook for subclasses.

        This method is called in all pseudo-constructors (clone, readObject) after HashMap has been initialized but before any entries have been inserted. (In the absence of this method, readObject would require explicit knowledge of subclasses.)

      • maskNull

        static <T> T maskNull​(T key)
        Returns internal representation for key. Use NULL_KEY if key is null.
      • isNull

        static <T> boolean isNull​(T key)
      • unmaskNull

        static <T> T unmaskNull​(T key)
        Returns key represented by specified internal representation.
      • hash

        static int hash​(java.lang.Object x)
        Returns a hash value for the specified object. In addition to the object's own hashCode, this method applies a "supplemental hash function," which defends against poor quality hash functions. This is critical because HashMap uses power-of two length hash tables.

        The shift distances in this function were chosen as the result of an automated search over the entire four-dimensional search space.

      • eq

        static boolean eq​(java.lang.Object x,
                          java.lang.Object y)
        Check for equality of non-null reference x and possibly-null y.
      • indexFor

        static int indexFor​(int h,
                            int length)
        Returns index for hash code h.
      • size

        public int size()
        Returns the number of key-value mappings in this map.
        Specified by:
        size in interface java.util.Map<K,​V>
        Overrides:
        size in class java.util.AbstractMap<K,​V>
        Returns:
        the number of key-value mappings in this map.
      • isEmpty

        public boolean isEmpty()
        Returns true if this map contains no key-value mappings.
        Specified by:
        isEmpty in interface java.util.Map<K,​V>
        Overrides:
        isEmpty in class java.util.AbstractMap<K,​V>
        Returns:
        true if this map contains no key-value mappings.
      • keyComparatorHash

        int keyComparatorHash​(K k)
      • hash

        int hash​(int h)
      • keyComparatorEq

        boolean keyComparatorEq​(K x,
                                K y)
        Check for equality of non-null reference x and possibly-null y.
      • get

        public V get​(java.lang.Object key)
        Returns the value to which the specified key is mapped in this identity hash map, or null if the map contains no mapping for this key. A return value of null does not necessarily indicate that the map contains no mapping for the key; it is also possible that the map explicitly maps the key to null. The containsKey method may be used to distinguish these two cases.
        Specified by:
        get in interface java.util.Map<K,​V>
        Overrides:
        get in class java.util.AbstractMap<K,​V>
        Parameters:
        key - the key whose associated value is to be returned.
        Returns:
        the value to which this map maps the specified key, or null if the map contains no mapping for this key.
        See Also:
        put(Object, Object)
      • containsKey

        public boolean containsKey​(java.lang.Object key)
        Returns true if this map contains a mapping for the specified key.
        Specified by:
        containsKey in interface java.util.Map<K,​V>
        Overrides:
        containsKey in class java.util.AbstractMap<K,​V>
        Parameters:
        key - The key whose presence in this map is to be tested
        Returns:
        true if this map contains a mapping for the specified key.
      • getEntry

        KeyComparatorHashMap.Entry<K,​V> getEntry​(K key)
        Returns the entry associated with the specified key in the HashMap. Returns null if the HashMap contains no mapping for this key.
      • put

        public V put​(K key,
                     V value)
        Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.
        Specified by:
        put in interface java.util.Map<K,​V>
        Overrides:
        put in class java.util.AbstractMap<K,​V>
        Parameters:
        key - key with which the specified value is to be associated.
        value - value to be associated with the specified key.
        Returns:
        previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the HashMap previously associated null with the specified key.
      • putForCreate

        private void putForCreate​(K key,
                                  V value)
        This method is used instead of put by constructors and pseudoconstructors (clone, readObject). It does not resize the table, check for comodification, etc. It calls createEntry rather than addEntry.
      • putAllForCreate

        private void putAllForCreate​(java.util.Map<? extends K,​? extends V> m)
      • resize

        void resize​(int newCapacity)
        Rehashes the contents of this map into a new array with a larger capacity. This method is called automatically when the number of keys in this map reaches its threshold.

        If current capacity is MAXIMUM_CAPACITY, this method does not resize the map, but sets threshold to Integer.MAX_VALUE. This has the effect of preventing future calls.

        Parameters:
        newCapacity - the new capacity, MUST be a power of two; must be greater than current capacity unless current capacity is MAXIMUM_CAPACITY (in which case value is irrelevant).
      • putAll

        public void putAll​(java.util.Map<? extends K,​? extends V> m)
        Copies all of the mappings from the specified map to this map These mappings will replace any mappings that this map had for any of the keys currently in the specified map.
        Specified by:
        putAll in interface java.util.Map<K,​V>
        Overrides:
        putAll in class java.util.AbstractMap<K,​V>
        Parameters:
        m - mappings to be stored in this map.
        Throws:
        java.lang.NullPointerException - if the specified map is null.
      • remove

        public V remove​(java.lang.Object key)
        Removes the mapping for this key from this map if present.
        Specified by:
        remove in interface java.util.Map<K,​V>
        Overrides:
        remove in class java.util.AbstractMap<K,​V>
        Parameters:
        key - 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.
      • removeEntryForKey

        KeyComparatorHashMap.Entry<K,​V> removeEntryForKey​(java.lang.Object key)
        Removes and returns the entry associated with the specified key in the HashMap. Returns null if the HashMap contains no mapping for this key.
      • clear

        public void clear()
        Removes all mappings from this map.
        Specified by:
        clear in interface java.util.Map<K,​V>
        Overrides:
        clear in class java.util.AbstractMap<K,​V>
      • containsValue

        public boolean containsValue​(java.lang.Object value)
        Returns true if this map maps one or more keys to the specified value.
        Specified by:
        containsValue in interface java.util.Map<K,​V>
        Overrides:
        containsValue in class java.util.AbstractMap<K,​V>
        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.
      • containsNullValue

        private boolean containsNullValue()
        Special-case code for containsValue with null argument
      • clone

        public java.lang.Object clone()
        Returns a shallow copy of this HashMap instance: the keys and values themselves are not cloned.
        Overrides:
        clone in class java.util.AbstractMap<K,​V>
        Returns:
        a shallow copy of this map.
      • addEntry

        void addEntry​(int hash,
                      K key,
                      V value,
                      int bucketIndex)
        Add a new entry with the specified key, value and hash code to the specified bucket. It is the responsibility of this method to resize the table if appropriate.

        Subclass overrides this to alter the behavior of put method.

      • createEntry

        void createEntry​(int hash,
                         K key,
                         V value,
                         int bucketIndex)
        Like addEntry except that this version is used when creating entries as part of Map construction or "pseudo-construction" (cloning, deserialization). This version needn't worry about resizing the table.

        Subclass overrides this to alter the behavior of HashMap(Map), clone, and readObject.

      • newKeyIterator

        java.util.Iterator<K> newKeyIterator()
      • newValueIterator

        java.util.Iterator<V> newValueIterator()
      • newEntryIterator

        java.util.Iterator<java.util.Map.Entry<K,​V>> newEntryIterator()
      • entrySet

        public java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
        Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. 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.
        Specified by:
        entrySet in interface java.util.Map<K,​V>
        Specified by:
        entrySet in class java.util.AbstractMap<K,​V>
        Returns:
        a collection view of the mappings contained in this map.
      • writeObject

        private void writeObject​(java.io.ObjectOutputStream s)
                          throws java.io.IOException
        Save the state of the HashMap instance to a stream (i.e., serialize it).
        Throws:
        java.io.IOException
      • readObject

        private void readObject​(java.io.ObjectInputStream s)
                         throws java.io.IOException,
                                java.lang.ClassNotFoundException
        Reconstitute the HashMap instance from a stream (i.e., deserialize it).
        Throws:
        java.io.IOException
        java.lang.ClassNotFoundException
      • capacity

        int capacity()
      • loadFactor

        float loadFactor()