Package org.apache.commons.collections4.list

Class TreeList<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractList<E>
org.apache.commons.collections4.list.TreeList<E>
All Implemented Interfaces:
Iterable<E>, Collection<E>, List<E>
public class TreeList<E> extends AbstractList<E>
A List implementation that is optimized for fast insertions and removals at any index in the list.

This list implementation utilises a tree structure internally to ensure that all insertions and removals are O(log n). This provides much faster performance than both an ArrayList and a LinkedList where elements are inserted and removed repeatedly from anywhere in the list.

The following relative performance statistics are indicative of this class: 

              get  add  insert  iterate  remove
 TreeList       3    5       1       2       1
 ArrayList      1    1      40       1      40
 LinkedList  5800    1     350       2     325

ArrayList is a good general purpose list implementation. It is faster than TreeList for most operations except inserting and removing in the middle of the list. ArrayList also uses less memory as TreeList uses one object per entry.

LinkedList is rarely a good choice of implementation. TreeList is almost always a good replacement for it, although it does use slightly more memory.

Since:
3.1

  • Constructor Details

    • TreeList

      public TreeList()
      Constructs a new empty list.

    • TreeList

      public TreeList(Collection<? extends E> coll)
      Constructs a new empty list that copies the specified collection.
      Parameters:
      coll - the collection to copy
      Throws:
      NullPointerException - if the collection is null

  • Method Details

    • add

      public void add(int index, E obj)
      Adds a new element to the list.
      Specified by:
      add in interface List<E>
      Overrides:
      add in class AbstractList<E>
      Parameters:
      index - the index to add before
      obj - the element to add

    • addAll

      public boolean addAll(Collection<? extends E> c)
      Appends all the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's Iterator.

      This method runs in O(n + log m) time, where m is the size of this list and n is the size of c.

      Specified by:
      addAll in interface Collection<E>
      Specified by:
      addAll in interface List<E>
      Overrides:
      addAll in class AbstractCollection<E>
      Parameters:
      c - the collection to be added to this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      NullPointerException

    • clear

      public void clear()
      Clears the list, removing all entries.
      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface List<E>
      Overrides:
      clear in class AbstractList<E>

    • contains

      public boolean contains(Object object)
      Searches for the presence of an object in the list.
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface List<E>
      Overrides:
      contains in class AbstractCollection<E>
      Parameters:
      object - the object to check
      Returns:
      true if the object is found

    • get

      public E get(int index)
      Gets the element at the specified index.
      Specified by:
      get in interface List<E>
      Specified by:
      get in class AbstractList<E>
      Parameters:
      index - the index to retrieve
      Returns:
      the element at the specified index

    • indexOf

      public int indexOf(Object object)
      Searches for the index of an object in the list.
      Specified by:
      indexOf in interface List<E>
      Overrides:
      indexOf in class AbstractList<E>
      Parameters:
      object - the object to search
      Returns:
      the index of the object, -1 if not found

    • iterator

      public Iterator<E> iterator()
      Gets an iterator over the list.
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface List<E>
      Overrides:
      iterator in class AbstractList<E>
      Returns:
      an iterator over the list

    • listIterator

      public ListIterator<E> listIterator()
      Gets a ListIterator over the list.
      Specified by:
      listIterator in interface List<E>
      Overrides:
      listIterator in class AbstractList<E>
      Returns:
      the new iterator

    • listIterator

      public ListIterator<E> listIterator(int fromIndex)
      Gets a ListIterator over the list.
      Specified by:
      listIterator in interface List<E>
      Overrides:
      listIterator in class AbstractList<E>
      Parameters:
      fromIndex - the index to start from
      Returns:
      the new iterator

    • remove

      public E remove(int index)
      Removes the element at the specified index.
      Specified by:
      remove in interface List<E>
      Overrides:
      remove in class AbstractList<E>
      Parameters:
      index - the index to remove
      Returns:
      the previous object at that index

    • set

      public E set(int index, E obj)
      Sets the element at the specified index.
      Specified by:
      set in interface List<E>
      Overrides:
      set in class AbstractList<E>
      Parameters:
      index - the index to set
      obj - the object to store at the specified index
      Returns:
      the previous object at that index
      Throws:
      IndexOutOfBoundsException - if the index is invalid

    • size

      public int size()
      Gets the current size of the list.
      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface List<E>
      Specified by:
      size in class AbstractCollection<E>
      Returns:
      the current size

    • toArray

      public Object[] toArray()
      Converts the list into an array.
      Specified by:
      toArray in interface Collection<E>
      Specified by:
      toArray in interface List<E>
      Overrides:
      toArray in class AbstractCollection<E>
      Returns:
      the list as an array