Package com.macrofocus.utils

Class AbstractMap<K,​V>

  • Type Parameters:
    K - the type of keys maintained by this map
    V - the type of mapped values
    All Implemented Interfaces:
    java.util.Map<K,​V>
    Direct Known Subclasses:
    IndexedTreeMap
    public abstract class AbstractMap<K,​V>
extends java.lang.Object
implements java.util.Map<K,​V>
    This class provides a skeletal implementation of the Map interface, to minimize the effort required to implement this interface.

    To implement an unmodifiable map, the programmer needs only to extend this class and provide an implementation for the entrySet method, which returns a set-view of the map's mappings. Typically, the returned set will, in turn, be implemented atop AbstractSet. This set should not support the add or remove methods, and its iterator should not support the remove method.

    To implement a modifiable map, the programmer must additionally override this class's put method (which otherwise throws an UnsupportedOperationException), and the iterator returned by entrySet().iterator() must additionally implement its remove method.

    The programmer should generally provide a void (no argument) and map constructor, as per the recommendation in the Map interface specification.

    The documentation for each non-abstract method in this class describes its implementation in detail. Each of these methods may be overridden if the map being implemented admits a more efficient implementation.

    This class is a member of the Java Collections Framework.

    Since:
    1.2
    See Also:
    Map, Collection

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  AbstractMap.SimpleEntry<K,​V>
      An Entry maintaining a key and a value.
      static class  AbstractMap.SimpleImmutableEntry<K,​V>
      An Entry maintaining an immutable key and value.

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

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

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected AbstractMap()
      Sole constructor.

    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      boolean containsKey​(java.lang.Object key)
      boolean containsValue​(java.lang.Object value)
      abstract java.util.Set<java.util.Map.Entry<K,​V>> entrySet()  
      boolean equals​(java.lang.Object o)
      Compares the specified object with this map for equality.
      V get​(java.lang.Object key)
      int hashCode()
      Returns the hash code value for this map.
      boolean isEmpty()
      java.util.Set<K> keySet()
      V put​(K key, V value)
      void putAll​(java.util.Map<? extends K,​? extends V> m)
      V remove​(java.lang.Object key)
      int size()
      java.lang.String toString()
      Returns a string representation of this map.
      java.util.Collection<V> values()

      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Map

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

    • Constructor Detail

      • AbstractMap

        protected AbstractMap()
        Sole constructor. (For invocation by subclass constructors, typically implicit.)

    • Method Detail

      • size

        public int size()

        This implementation returns entrySet().size().

        Specified by:
        size in interface java.util.Map<K,​V>

      • isEmpty

        public boolean isEmpty()

        This implementation returns size() == 0.

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

      • containsValue

        public boolean containsValue​(java.lang.Object value)

        This implementation iterates over entrySet() searching for an entry with the specified value. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map.

        Specified by:
        containsValue in interface java.util.Map<K,​V>
        Throws:
        java.lang.ClassCastException
        java.lang.NullPointerException

      • containsKey

        public boolean containsKey​(java.lang.Object key)

        This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, true is returned. If the iteration terminates without finding such an entry, false is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

        Specified by:
        containsKey in interface java.util.Map<K,​V>
        Throws:
        java.lang.ClassCastException
        java.lang.NullPointerException

      • get

        public V get​(java.lang.Object key)

        This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, the entry's value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

        Specified by:
        get in interface java.util.Map<K,​V>
        Throws:
        java.lang.ClassCastException
        java.lang.NullPointerException

      • put

        public V put​(K key,
             V value)

        This implementation always throws an UnsupportedOperationException.

        Specified by:
        put in interface java.util.Map<K,​V>
        Throws:
        java.lang.UnsupportedOperationException
        java.lang.ClassCastException
        java.lang.NullPointerException
        java.lang.IllegalArgumentException

      • remove

        public V remove​(java.lang.Object key)

        This implementation iterates over entrySet() searching for an entry with the specified key. If such an entry is found, its value is obtained with its getValue operation, the entry is removed from the collection (and the backing map) with the iterator's remove operation, and the saved value is returned. If the iteration terminates without finding such an entry, null is returned. Note that this implementation requires linear time in the size of the map; many implementations will override this method.

        Note that this implementation throws an UnsupportedOperationException if the entrySet iterator does not support the remove method and this map contains a mapping for the specified key.

        Specified by:
        remove in interface java.util.Map<K,​V>
        Throws:
        java.lang.UnsupportedOperationException
        java.lang.ClassCastException
        java.lang.NullPointerException

      • putAll

        public void putAll​(java.util.Map<? extends K,​? extends V> m)

        This implementation iterates over the specified map's entrySet() collection, and calls this map's put operation once for each entry returned by the iteration.

        Note that this implementation throws an UnsupportedOperationException if this map does not support the put operation and the specified map is nonempty.

        Specified by:
        putAll in interface java.util.Map<K,​V>
        Throws:
        java.lang.UnsupportedOperationException
        java.lang.ClassCastException
        java.lang.NullPointerException
        java.lang.IllegalArgumentException

      • clear

        public void clear()

        This implementation calls entrySet().clear().

        Note that this implementation throws an UnsupportedOperationException if the entrySet does not support the clear operation.

        Specified by:
        clear in interface java.util.Map<K,​V>
        Throws:
        java.lang.UnsupportedOperationException

      • keySet

        public java.util.Set<K> keySet()

        This implementation returns a set that subclasses AbstractSet. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsKey method.

        The set is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same set.

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

      • values

        public java.util.Collection<V> values()

        This implementation returns a collection that subclasses AbstractCollection. The subclass's iterator method returns a "wrapper object" over this map's entrySet() iterator. The size method delegates to this map's size method and the contains method delegates to this map's containsValue method.

        The collection is created the first time this method is called, and returned in response to all subsequent calls. No synchronization is performed, so there is a slight chance that multiple calls to this method will not all return the same collection.

        Specified by:
        values in interface java.util.Map<K,​V>

      • entrySet

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

      • equals

        public boolean equals​(java.lang.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.

        This implementation first checks if the specified object is this map; if so it returns true. Then, it checks if the specified object is a map whose size is identical to the size of this map; if not, it returns false. If so, it iterates over this map's entrySet collection, and checks that the specified map contains each mapping that this map contains. If the specified map fails to contain such a mapping, false is returned. If the iteration completes, true is returned.

        Specified by:
        equals in interface java.util.Map<K,​V>
        Overrides:
        equals in class java.lang.Object
        Parameters:
        o - object to be compared for equality with this map
        Returns:
        true if the specified object is equal to this map

      • hashCode

        public int hashCode()
        Returns the hash code value for this map. The hash code of a map is defined to be the sum of the hash codes of each entry in the map's entrySet() view. This ensures that 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().

        This implementation iterates over entrySet(), calling hashCode() on each element (entry) in the set, and adding up the results.

        Specified by:
        hashCode in interface java.util.Map<K,​V>
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        the hash code value for this map
        See Also:
        Map.Entry.hashCode(), Object.equals(Object), Set.equals(Object)

      • toString

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