org.apache.commons.math3.geometry.partitioning.utilities

## Class AVLTree<T extends Comparable<T>>

- java.lang.Object
- - org.apache.commons.math3.geometry.partitioning.utilities.AVLTree<T>

- Type Parameters:
    `T` - the type of the elements

      public class AVLTree<T extends Comparable<T>>
      extends Object

  This class implements AVL trees.

  The purpose of this class is to sort elements while allowing duplicate elements (i.e. such that `a.equals(b)` is true). The `SortedSet` interface does not allow this, so a specific class is needed. Null elements are not allowed.

  Since the `equals` method is not sufficient to differentiate elements, the `delete` method is implemented using the equality operator.

  In order to clearly mark the methods provided here do not have the same semantics as the ones specified in the `SortedSet` interface, different names are used (`add` has been replaced by `insert` and `remove` has been replaced by `delete`).

  This class is based on the C implementation Georg Kraml has put in the public domain. Unfortunately, his page seems not to exist any more.

  Since:
    3.0
  Version:
    $Id: AVLTree.java 1416643 2012-12-03 19:37:14Z tn $

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `class` | `AVLTree.Node` This class implements AVL trees nodes.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `AVLTree()` Build an empty tree.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `delete(T element)` Delete an element from the tree.
    `AVLTree.Node` | `getLargest()` Get the node whose element is the largest one in the tree.
    `AVLTree.Node` | `getNotLarger(T reference)` Get the node whose element is not larger than the reference object.
    `AVLTree.Node` | `getNotSmaller(T reference)` Get the node whose element is not smaller than the reference object.
    `AVLTree.Node` | `getSmallest()` Get the node whose element is the smallest one in the tree.
    `void` | `insert(T element)` Insert an element in the tree.
    `boolean` | `isEmpty()` Check if the tree is empty.
    `int` | `size()` Get the number of elements of the tree.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### AVLTree

          public AVLTree()

      Build an empty tree.

  - ### Method Detail

    - #### insert

          public void insert(T element)

      Insert an element in the tree.
      Parameters:
        `element` - element to insert (silently ignored if null)

    - #### delete

          public boolean delete(T element)

      Delete an element from the tree.

      The element is deleted only if there is a node `n` containing exactly the element instance specified, i.e. for which `n.getElement() == element`. This is purposely different from the specification of the `java.util.Set` `remove` method (in fact, this is the reason why a specific class has been developed).

      Parameters:
        `element` - element to delete (silently ignored if null)
      Returns:
        true if the element was deleted from the tree

    - #### isEmpty

          public boolean isEmpty()

      Check if the tree is empty.
      Returns:
        true if the tree is empty

    - #### size

          public int size()

      Get the number of elements of the tree.
      Returns:
        number of elements contained in the tree

    - #### getSmallest

          public AVLTree.Node getSmallest()

      Get the node whose element is the smallest one in the tree.
      Returns:
        the tree node containing the smallest element in the tree or null if the tree is empty
      See Also:
        `getLargest()`, `getNotSmaller(T)`, `getNotLarger(T)`, `AVLTree.Node.getPrevious()`, `AVLTree.Node.getNext()`

    - #### getLargest

          public AVLTree.Node getLargest()

      Get the node whose element is the largest one in the tree.
      Returns:
        the tree node containing the largest element in the tree or null if the tree is empty
      See Also:
        `getSmallest()`, `getNotSmaller(T)`, `getNotLarger(T)`, `AVLTree.Node.getPrevious()`, `AVLTree.Node.getNext()`

    - #### getNotSmaller

          public AVLTree.Node getNotSmaller(T reference)

      Get the node whose element is not smaller than the reference object.
      Parameters:
        `reference` - reference object (may not be in the tree)
      Returns:
        the tree node containing the smallest element not smaller than the reference object or null if either the tree is empty or all its elements are smaller than the reference object
      See Also:
        `getSmallest()`, `getLargest()`, `getNotLarger(T)`, `AVLTree.Node.getPrevious()`, `AVLTree.Node.getNext()`

    - #### getNotLarger

          public AVLTree.Node getNotLarger(T reference)

      Get the node whose element is not larger than the reference object.
      Parameters:
        `reference` - reference object (may not be in the tree)
      Returns:
        the tree node containing the largest element not larger than the reference object (in which case the node is guaranteed not to be empty) or null if either the tree is empty or all its elements are larger than the reference object
      See Also:
        `getSmallest()`, `getLargest()`, `getNotSmaller(T)`, `AVLTree.Node.getPrevious()`, `AVLTree.Node.getNext()`

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