Module org.apache.sis.util
Package org.apache.sis.util.collection

Class FrequencySortedSet<E>

Object
AbstractCollection<E>
AbstractSet<E>
FrequencySortedSet<E>
Type Parameters:
E - the type of elements in the set.
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, Comparator<E>, Sequenced­Collection<E>, Sequenced­Set<E>, Set<E>, Sorted­Set<E>
public class FrequencySortedSet<E> extends AbstractSet<E> implements SortedSet<E>, Comparator<E>, Serializable
A set with elements ordered by the amount of time they were added. By default, less frequently added elements are first and most frequently added elements are last. If some elements were added the same amount of time, then the iterator will traverse them in their insertion order.

An optional boolean argument in the constructor allows the construction of set in reversed order (most frequently added elements first, less frequently added last). This is similar but not identical to creating a default Frequency­Sorted­Set and iterating through it in reverse order. The difference is that elements added the same amount of time will still be traversed in their insertion order.

This class is not thread-safe. Synchronizations (if wanted) are caller responsibility.

Since:
0.8
See Also:

  • Constructor Details

    • FrequencySortedSet

      public FrequencySortedSet()
      Creates an initially empty set with less frequent elements first.

    • FrequencySortedSet

      public FrequencySortedSet(boolean reversed)
      Creates an initially empty set with the default initial capacity.
      Parameters:
      reversed - true if the elements should be sorted in reverse order (most frequent element first, less frequent element last).

    • FrequencySortedSet

      public FrequencySortedSet(int initialCapacity, boolean reversed)
      Creates an initially empty set with the specified initial capacity.
      Parameters:
      initial­Capacity - the initial capacity.
      reversed - true if the elements should be sorted in reverse order (most frequent element first, less frequent element last).

  • Method Details

    • size

      public int size()
      Returns the number of elements in this set.
      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface Set<E>
      Specified by:
      size in class Abstract­Collection<E>

    • isEmpty

      public boolean isEmpty()
      Returns true if this set is empty.
      Specified by:
      is­Empty in interface Collection<E>
      Specified by:
      is­Empty in interface Set<E>
      Overrides:
      is­Empty in class Abstract­Collection<E>

    • add

      public boolean add(E element, int occurrence) throws IllegalArgumentException
      Repetitively adds the specified element to this set. Returns true if this set changed as a result of this operation. Changes in element order are not notified by the returned value.
      Parameters:
      element - the element to add (may be null).
      occurrence - the number of time to add the given element. The default value is 1.
      Returns:
      true if this set changed as a result of this operation.
      Throws:
      Illegal­Argument­Exception - if occurrence is negative.

    • add

      public boolean add(E element)
      Adds the specified element to this set. Returns true if this set changed as a result of this operation. Changes in element order are not notified by the returned value.

      The default implementation delegates to add(element, 1).

      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface Set<E>
      Overrides:
      add in class Abstract­Collection<E>
      Parameters:
      element - the element to add (may be null).
      Returns:
      true if this set changed as a result of this operation.

    • contains

      public boolean contains(Object element)
      Returns true if this set contains the specified element.
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface Set<E>
      Overrides:
      contains in class Abstract­Collection<E>
      Parameters:
      element - the element whose presence in this set is to be tested.
      Returns:
      true if this set contains the specified element.

    • remove

      public boolean remove(Object element)
      Removes the specified element from this set, no matter how many time it has been added. Returns true if this set changed as a result of this operation.
      Specified by:
      remove in interface Collection<E>
      Specified by:
      remove in interface Set<E>
      Overrides:
      remove in class Abstract­Collection<E>
      Parameters:
      element - the element to remove.
      Returns:
      true if this set changed as a result of this operation.

    • clear

      public void clear()
      Removes all elements from this set.
      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface Set<E>
      Overrides:
      clear in class Abstract­Collection<E>

    • iterator

      public Iterator<E> iterator()
      Returns an iterator over the elements in this set in frequency order.
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface Set<E>
      Specified by:
      iterator in class Abstract­Collection<E>

    • headSet

      public SortedSet<E> headSet(E toElement)
      Returns a view of the portion of this set whose elements occur with a frequency strictly less than to­Element frequency.
      Specified by:
      head­Set in interface Sorted­Set<E>
      Parameters:
      to­Element - high endpoint (exclusive) of the returned set. May be null.
      Returns:
      a view of the portion of this set delimited by the given endpoint.

    • tailSet

      public SortedSet<E> tailSet(E fromElement)
      Returns a view of the portion of this set whose elements occur with a frequency equal or greater than from­Element frequency.
      Specified by:
      tail­Set in interface Sorted­Set<E>
      Parameters:
      from­Element - low endpoint (inclusive) of the returned set. May be null.
      Returns:
      a view of the portion of this set delimited by the given endpoint.

    • subSet

      public SortedSet<E> subSet(E fromElement, E toElement)
      Returns a view of the portion of this set whose elements occur with a frequency in the range of from­Element frequency inclusive to to­Element frequency exclusive.
      Specified by:
      sub­Set in interface Sorted­Set<E>
      Parameters:
      from­Element - low endpoint (inclusive) of the returned set. May be null.
      to­Element - high endpoint (exclusive) of the returned set. May be null.
      Returns:
      a view of the portion of this set delimited by the given endpoints.

    • first

      public E first() throws NoSuchElementException
      Returns the first element in this set.
      • For sets created with the default order, this is the less frequently added element. If more than one element were added with the same frequency, this is the first one that has been added to this set at this frequency.
      • For sets created with the reverse order, this is the most frequently added element. If more than one element were added with the same frequency, this is the first one that has been added to this set at this frequency.
      Specified by:
      first in interface Sorted­Set<E>
      Throws:
      No­Such­Element­Exception - if this set is empty.

    • last

      public E last() throws NoSuchElementException
      Returns the last element in this set.
      • For sets created with the default order, this is the most frequently added element. If more than one element were added with the same frequency, this is the last one that has been added to this set at this frequency.
      • For sets created with the reverse order, this is the less frequently added element. If more than one element were added with the same frequency, this is the last one that has been added to this set at this frequency.
      Specified by:
      last in interface Sorted­Set<E>
      Throws:
      No­Such­Element­Exception - if this set is empty.

    • comparator

      public final Comparator<E> comparator()
      Returns the comparator used to order the elements in this set. For a Frequency­Sorted­Set, the comparator is always this.

      This method is final because the Frequency­Sorted­Set implementation makes assumptions on the comparator that would not hold if this method were overridden.

      Specified by:
      comparator in interface Sorted­Set<E>

    • compare

      public final int compare(E o1, E o2)
      Compares the specified elements for frequency. For Frequency­Sorted­Set with default ordering, this method returns a positive number if o1 has been added more frequently to this set than o2, a negative number if o1 has been added less frequently than o2, and 0 otherwise. For Frequency­Sorted­Set with reverse ordering, this is the converse.

      This method is final because the Frequency­Sorted­Set implementation makes assumptions on the comparator that would not hold if this method were overridden.

      Specified by:
      compare in interface Comparator<E>

    • frequency

      public int frequency(E element)
      Returns the frequency of the specified element in this set.
      Parameters:
      element - the element whose frequency is to be obtained.
      Returns:
      the frequency of the given element, or 0 if it does not occur in this set.

    • frequencies

      public int[] frequencies()
      Returns the frequency of all elements in this set, in iteration order.
      Returns:
      the frequency of all elements in this set.

    • toArray

      public Object[] toArray()
      Returns the content of this set as an array.
      Specified by:
      to­Array in interface Collection<E>
      Specified by:
      to­Array in interface Set<E>
      Overrides:
      to­Array in class Abstract­Collection<E>

    • toArray

      public <T> T[] toArray(T[] array)
      Returns the content of this set as an array.
      Specified by:
      to­Array in interface Collection<E>
      Specified by:
      to­Array in interface Set<E>
      Overrides:
      to­Array in class Abstract­Collection<E>
      Type Parameters:
      T - the type of the array elements.
      Parameters:
      array - the array where to copy the elements.
      Returns:
      the elements in the given array, or in a new array if the given array does not have a sufficient capacity.