Package org.apache.commons.collections4.list

Class TreeList<E>

  • All Implemented Interfaces:
    Iterable<E>, Collection<E>, List<E>
    public class TreeList<E>
extends AbstractList<E>
    A List implementation that is optimised 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 Detail

      • 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 Detail

      • 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

      • 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

      • 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

      • 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

      • 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 of 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

      • 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

      • 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