Package org.htmlunit.util

Class OrderedFastHashMap<K,​V>

  • Type Parameters:
    K - the type of the key
    V - the type of the value
    All Implemented Interfaces:
    java.io.Serializable, java.util.Map<K,​V>
    public class OrderedFastHashMap<K,​V>
extends java.lang.Object
implements java.util.Map<K,​V>, java.io.Serializable
    Simple and efficient linked map or better ordered map implementation to replace the default linked list which is heavy. This map does not support null and it is not thread-safe. It implements the map interface but only for compatibility reason in the sense of replacing a regular map. Iterator and streaming methods are either not implemented or less efficient. It goes the extra mile to avoid the overhead of wrapper objects. Because you typically know what you do, we run minimal index checks only and rely on the default exceptions by Java. Why should we do things twice? Important Note: This is meant for small maps because to save on memory allocation and churn, we are not keeping a wrapper for a reference from the map to the list, only from the list to the map. Hence when you remove a key, we have to iterate the entire list. Mostly, half of it most likely, but still expensive enough. When you have something small like 10 to 20 entries, this won't matter that much especially when a remove might be a rare event. This is based on FashHashMap from XLT which is based on a version from: https://github.com/mikvor/hashmapTest/blob/master/src/main/java/map/objobj/ObjObjMap.java No concrete license specified at the source. The project is public domain.
    See Also:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      OrderedFastHashMap()
      Default constructor which create an ordered map with default size.
      OrderedFastHashMap​(int size)
      Custom constructor to get a map with a custom size and fill factor.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      V add​(K key, V value)  
      V addFirst​(K key, V value)  
      V addLast​(K key, V value)  
      void clear()
      Clears the map, reuses the data structure by clearing it out.
      boolean containsKey​(java.lang.Object key)
      Checks of a key is in the map.
      boolean containsValue​(java.lang.Object value)  
      java.util.Set<java.util.Map.Entry<K,​V>> entrySet()  
      V get​(java.lang.Object key)
      Get a value for a key, any key type is permitted due to the nature of the Map interface.
      org.htmlunit.util.OrderedFastHashMap.Entry<K,​V> getEntry​(int index)
      Returns an entry consisting of key and value at a given position.
      V getFirst()  
      K getKey​(int index)
      Returns the key at a certain position of the ordered list that keeps the addition order of this map.
      V getLast()  
      V getValue​(int index)
      Returns the value at a certain position of the ordered list that keeps the addition order of this map.
      boolean isEmpty()  
      java.util.List<K> keys()
      Returns a list of all keys in order of addition.
      java.util.Set<K> keySet()  
      V put​(K key, V value)  
      void putAll​(java.util.Map<? extends K,​? extends V> src)  
      V remove​(int index)
      Removes a key and value from this map based on the position in the backing list, rather by key as usual.
      V remove​(java.lang.Object key)
      Remove a key from the map.
      V removeFirst()  
      V removeLast()  
      void reverse()
      Just reverses the ordering of the map as created so far.
      int size()
      Returns the size of the map, effectively the number of entries.
      java.lang.String toString()  
      java.util.List<V> values()
      Returns a list of all values ordered by when the key was added.

      • Methods inherited from class java.lang.Object

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

      • Methods inherited from interface java.util.Map

        compute, computeIfAbsent, computeIfPresent, equals, forEach, getOrDefault, hashCode, merge, putIfAbsent, remove, replace, replace, replaceAll

    • Constructor Detail

      • OrderedFastHashMap

        public OrderedFastHashMap()
        Default constructor which create an ordered map with default size.

      • OrderedFastHashMap

        public OrderedFastHashMap​(int size)
        Custom constructor to get a map with a custom size and fill factor. We are not spending time on range checks, rather use a default if things are wrong.
        Parameters:
        size - the size to use, must 0 or positive, negative values default to 0

    • Method Detail

      • get

        public V get​(java.lang.Object key)
        Get a value for a key, any key type is permitted due to the nature of the Map interface.
        Specified by:
        get in interface java.util.Map<K,​V>
        Parameters:
        key - the key
        Returns:
        the value or null, if the key does not exist

      • remove

        public V remove​(java.lang.Object key)
        Remove a key from the map. Returns the stored value or null of the key is not known.
        Specified by:
        remove in interface java.util.Map<K,​V>
        Parameters:
        key - the key to remove
        Returns:
        the stored value or null if the key does not exist

      • size

        public int size()
        Returns the size of the map, effectively the number of entries.
        Specified by:
        size in interface java.util.Map<K,​V>
        Returns:
        the size of the map

      • keys

        public java.util.List<K> keys()
        Returns a list of all keys in order of addition. This is an expensive operation, because we get a static list back that is not backed by the implementation. Changes to the returned list are not reflected in the map.
        Returns:
        a list of keys as inserted into the map

      • values

        public java.util.List<V> values()
        Returns a list of all values ordered by when the key was added. This is an expensive operation, because we get a static list back that is not backed by the implementation. Changes to the returned list are not reflected in the map.
        Specified by:
        values in interface java.util.Map<K,​V>
        Returns:
        a list of values

      • clear

        public void clear()
        Clears the map, reuses the data structure by clearing it out. It won't shrink the underlying arrays!
        Specified by:
        clear in interface java.util.Map<K,​V>

      • getEntry

        public org.htmlunit.util.OrderedFastHashMap.Entry<K,​V> getEntry​(int index)
        Returns an entry consisting of key and value at a given position. This position relates to the ordered key list that maintain the addition order for this map.
        Parameters:
        index - the position to fetch
        Returns:
        an entry of key and value
        Throws:
        java.lang.IndexOutOfBoundsException - when the ask for the position is invalid

      • getKey

        public K getKey​(int index)
        Returns the key at a certain position of the ordered list that keeps the addition order of this map.
        Parameters:
        index - the position to fetch
        Returns:
        the key at this position
        Throws:
        java.lang.IndexOutOfBoundsException - when the ask for the position is invalid

      • getValue

        public V getValue​(int index)
        Returns the value at a certain position of the ordered list that keeps the addition order of this map.
        Parameters:
        index - the position to fetch
        Returns:
        the value at this position
        Throws:
        java.lang.IndexOutOfBoundsException - when the ask for the position is invalid

      • remove

        public V remove​(int index)
        Removes a key and value from this map based on the position in the backing list, rather by key as usual.
        Parameters:
        index - the position to remove the data from
        Returns:
        the value stored
        Throws:
        java.lang.IndexOutOfBoundsException - when the ask for the position is invalid

      • put

        public V put​(K key,
             V value)
        Specified by:
        put in interface java.util.Map<K,​V>

      • addFirst

        public V addFirst​(K key,
                  V value)

      • add

        public V add​(K key,
             V value)

      • addLast

        public V addLast​(K key,
                 V value)

      • getFirst

        public V getFirst()

      • getLast

        public V getLast()

      • removeFirst

        public V removeFirst()

      • removeLast

        public V removeLast()

      • containsKey

        public boolean containsKey​(java.lang.Object key)
        Checks of a key is in the map.
        Specified by:
        containsKey in interface java.util.Map<K,​V>
        Parameters:
        key - the key to check
        Returns:
        true of the key is in the map, false otherwise

      • containsValue

        public boolean containsValue​(java.lang.Object value)
        Specified by:
        containsValue in interface java.util.Map<K,​V>

      • isEmpty

        public boolean isEmpty()
        Specified by:
        isEmpty in interface java.util.Map<K,​V>

      • entrySet

        public java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
        Specified by:
        entrySet in interface java.util.Map<K,​V>

      • keySet

        public java.util.Set<K> keySet()
        Specified by:
        keySet in interface java.util.Map<K,​V>

      • reverse

        public void reverse()
        Just reverses the ordering of the map as created so far.

      • putAll

        public void putAll​(java.util.Map<? extends K,​? extends V> src)
        Specified by:
        putAll in interface java.util.Map<K,​V>

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object