Module org.apache.commons.collections4
Package org.apache.commons.collections4.bag

Class AbstractMapBag<E>

java.lang.Object
org.apache.commons.collections4.bag.AbstractMapBag<E>
Type Parameters:
E - the type of elements in this bag
All Implemented Interfaces:
Iterable<E>, Collection<E>, Bag<E>
Direct Known Subclasses:
HashBag, TreeBag
public abstract class AbstractMapBag<E> extends Object implements Bag<E>
Abstract implementation of the Bag interface to simplify the creation of subclass implementations.

Subclasses specify a Map implementation to use as the internal storage. The map will be used to map bag elements to a number; the number represents the number of occurrences of that element in the bag.

Since:
3.0 (previously DefaultMapBag v2.0)

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected static class 
    AbstractMapBag.MutableInteger
    Mutable integer class for storing the data.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    AbstractMapBag()
    Constructor needed for subclass serialisation.
    protected
    AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map)
    Constructor that assigns the specified Map as the backing store.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(E object)
    Adds a new element to the bag, incrementing its count in the underlying map.
    boolean
    add(E object, int nCopies)
    Adds a new element to the bag, incrementing its count in the map.
    boolean
    addAll(Collection<? extends E> coll)
    Invokes add(Object) for each element in the given collection.
    void
    clear()
    Clears the bag by clearing the underlying map.
    boolean
    contains(Object object)
    Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
    boolean
    containsAll(Collection<?> coll)
    Determines if the bag contains the given elements.
    protected void
    doReadObject(Map<E,AbstractMapBag.MutableInteger> map, ObjectInputStream in)
    Read the map in using a custom routine.
    protected void
    doWriteObject(ObjectOutputStream out)
    Write the map out using a custom routine.
    boolean
    equals(Object object)
    Compares this Bag to another.
    int
    getCount(Object object)
    Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
    protected Map<E,AbstractMapBag.MutableInteger>
    getMap()
    Utility method for implementations to access the map that backs this bag.
    int
    hashCode()
    Gets a hash code for the Bag compatible with the definition of equals.
    boolean
    isEmpty()
    Returns true if the underlying map is empty.
    Iterator<E>
    iterator()
    Gets an iterator over the bag elements.
    boolean
    remove(Object object)
    Removes all copies of the specified object from the bag.
    boolean
    remove(Object object, int nCopies)
    Removes a specified number of copies of an object from the bag.
    boolean
    removeAll(Collection<?> coll)
    Removes objects from the bag according to their count in the specified collection.
    boolean
    retainAll(Collection<?> coll)
    Remove any members of the bag that are not in the given bag, respecting cardinality.
    int
    size()
    Returns the number of elements in this bag.
    Object[]
    toArray()
    Returns an array of all of this bag's elements.
    <T> T[]
    toArray(T[] array)
    Returns an array of all of this bag's elements.
    String
    toString()
    Implement a toString() method suitable for debugging.
    Set<E>
    uniqueSet()
    Returns an unmodifiable view of the underlying map's key set.

    Methods inherited from class java.lang.Object

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

    Methods inherited from interface java.util.Collection

    parallelStream, removeIf, spliterator, stream

    Methods inherited from interface java.lang.Iterable

    forEach

  • Constructor Details

    • AbstractMapBag

      protected AbstractMapBag()
      Constructor needed for subclass serialisation.

    • AbstractMapBag

      protected AbstractMapBag(Map<E,AbstractMapBag.MutableInteger> map)
      Constructor that assigns the specified Map as the backing store. The map must be empty and non-null.
      Parameters:
      map - the map to assign

  • Method Details

    • getMap

      protected Map<E,AbstractMapBag.MutableInteger> getMap()
      Utility method for implementations to access the map that backs this bag. Not intended for interactive use outside of subclasses.
      Returns:
      the map being used by the Bag

    • size

      public int size()
      Returns the number of elements in this bag.
      Specified by:
      size in interface Bag<E>
      Specified by:
      size in interface Collection<E>
      Returns:
      current size of the bag

    • isEmpty

      public boolean isEmpty()
      Returns true if the underlying map is empty.
      Specified by:
      isEmpty in interface Collection<E>
      Returns:
      true if bag is empty

    • getCount

      public int getCount(Object object)
      Returns the number of occurrence of the given element in this bag by looking up its count in the underlying map.
      Specified by:
      getCount in interface Bag<E>
      Parameters:
      object - the object to search for
      Returns:
      the number of occurrences of the object, zero if not found

    • contains

      public boolean contains(Object object)
      Determines if the bag contains the given element by checking if the underlying map contains the element as a key.
      Specified by:
      contains in interface Collection<E>
      Parameters:
      object - the object to search for
      Returns:
      true if the bag contains the given element

    • containsAll

      public boolean containsAll(Collection<?> coll)
      Determines if the bag contains the given elements.
      Specified by:
      containsAll in interface Bag<E>
      Specified by:
      containsAll in interface Collection<E>
      Parameters:
      coll - the collection to check against
      Returns:
      true if the Bag contains all the collection

    • iterator

      public Iterator<E> iterator()
      Gets an iterator over the bag elements. Elements present in the Bag more than once will be returned repeatedly.
      Specified by:
      iterator in interface Bag<E>
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Returns:
      the iterator

    • add

      public boolean add(E object)
      Adds a new element to the bag, incrementing its count in the underlying map.
      Specified by:
      add in interface Bag<E>
      Specified by:
      add in interface Collection<E>
      Parameters:
      object - the object to add
      Returns:
      true if the object was not already in the uniqueSet

    • add

      public boolean add(E object, int nCopies)
      Adds a new element to the bag, incrementing its count in the map.
      Specified by:
      add in interface Bag<E>
      Parameters:
      object - the object to search for
      nCopies - the number of copies to add
      Returns:
      true if the object was not already in the uniqueSet

    • addAll

      public boolean addAll(Collection<? extends E> coll)
      Invokes add(Object) for each element in the given collection.
      Specified by:
      addAll in interface Collection<E>
      Parameters:
      coll - the collection to add
      Returns:
      true if this call changed the bag

    • clear

      public void clear()
      Clears the bag by clearing the underlying map.
      Specified by:
      clear in interface Collection<E>

    • remove

      public boolean remove(Object object)
      Removes all copies of the specified object from the bag.
      Specified by:
      remove in interface Bag<E>
      Specified by:
      remove in interface Collection<E>
      Parameters:
      object - the object to remove
      Returns:
      true if the bag changed

    • remove

      public boolean remove(Object object, int nCopies)
      Removes a specified number of copies of an object from the bag.
      Specified by:
      remove in interface Bag<E>
      Parameters:
      object - the object to remove
      nCopies - the number of copies to remove
      Returns:
      true if the bag changed

    • removeAll

      public boolean removeAll(Collection<?> coll)
      Removes objects from the bag according to their count in the specified collection.
      Specified by:
      removeAll in interface Bag<E>
      Specified by:
      removeAll in interface Collection<E>
      Parameters:
      coll - the collection to use
      Returns:
      true if the bag changed

    • retainAll

      public boolean retainAll(Collection<?> coll)
      Remove any members of the bag that are not in the given bag, respecting cardinality.
      Specified by:
      retainAll in interface Bag<E>
      Specified by:
      retainAll in interface Collection<E>
      Parameters:
      coll - the collection to retain
      Returns:
      true if this call changed the collection

    • toArray

      public Object[] toArray()
      Returns an array of all of this bag's elements.
      Specified by:
      toArray in interface Collection<E>
      Returns:
      an array of all of this bag's elements

    • toArray

      public <T> T[] toArray(T[] array)
      Returns an array of all of this bag's elements. If the input array has more elements than are in the bag, trailing elements will be set to null.
      Specified by:
      toArray in interface Collection<E>
      Type Parameters:
      T - the type of the array elements
      Parameters:
      array - the array to populate
      Returns:
      an array of all of this bag's elements
      Throws:
      ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of the elements in this list
      NullPointerException - if the specified array is null

    • uniqueSet

      public Set<E> uniqueSet()
      Returns an unmodifiable view of the underlying map's key set.
      Specified by:
      uniqueSet in interface Bag<E>
      Returns:
      the set of unique elements in this bag

    • doWriteObject

      protected void doWriteObject(ObjectOutputStream out) throws IOException
      Write the map out using a custom routine.
      Parameters:
      out - the output stream
      Throws:
      IOException - any of the usual I/O related exceptions

    • doReadObject

      protected void doReadObject(Map<E,AbstractMapBag.MutableInteger> map, ObjectInputStream in) throws IOException, ClassNotFoundException
      Read the map in using a custom routine.
      Parameters:
      map - the map to use
      in - the input stream
      Throws:
      IOException - any of the usual I/O related exceptions
      ClassNotFoundException - if the stream contains an object which class can not be loaded
      ClassCastException - if the stream does not contain the correct objects

    • equals

      public boolean equals(Object object)
      Compares this Bag to another. This Bag equals another Bag if it contains the same number of occurrences of the same elements.
      Specified by:
      equals in interface Collection<E>
      Overrides:
      equals in class Object
      Parameters:
      object - the Bag to compare to
      Returns:
      true if equal

    • hashCode

      public int hashCode()
      Gets a hash code for the Bag compatible with the definition of equals. The hash code is defined as the sum total of a hash code for each element. The per element hash code is defined as (e==null ? 0 : e.hashCode()) ^ noOccurances). This hash code is compatible with the Set interface.
      Specified by:
      hashCode in interface Collection<E>
      Overrides:
      hashCode in class Object
      Returns:
      the hash code of the Bag

    • toString

      public String toString()
      Implement a toString() method suitable for debugging.
      Overrides:
      toString in class Object
      Returns:
      a debugging toString