【发布时间】：2018-06-05 18:42:51
【问题描述】：
如果我放了为什么会这样
tree.addElement(10, tree.root);
它可以工作，但如果我再做一次
tree.addElement(20, tree.root);
它不工作？我只想向树中添加元素。我的方法有什么问题？编译器给我的错误很简单：
LinkedBinarySearchTree.addElement(LinkedBinarySearchTree.java:68)
public void addElement(T element, BinaryTreeNode node)
{
if (!(element instanceof Comparable))
throw new NonComparableElementException("LinkedBinarySearchTree");
Comparable<T> comparableElement = (Comparable<T>)element;
if (isEmpty())
root = new BinaryTreeNode<T>(element);
else
{
if (comparableElement.compareTo(root.getElement()) < 0)
{
if (root.getLeft() == null)
this.getRootNode().setLeft(new BinaryTreeNode<T>(element));
else
addElement(element, root.getLeft());
}
else
{
if (root.getRight() == null)
this.getRootNode().setRight(new BinaryTreeNode<T>(element));
else
addElement(element, root.getRight());
}
}
modCount++;
}
下面是剩下的代码：
public class BinaryTreeNode<T>
{
protected T element;
protected BinaryTreeNode<T> left, right;
/**
* Creates a new tree node with the specified data.
*
* @param obj the element that will become a part of the new tree node
*/
public BinaryTreeNode(T obj)
{
element = obj;
left = null;
right = null;
}
/**
* Creates a new tree node with the specified data.
*
* @param obj the element that will become a part of the new tree node
* @param left the tree that will be the left subtree of this node
* @param right the tree that will be the right subtree of this node
*/
public BinaryTreeNode(T obj, LinkedBinaryTree<T> left, LinkedBinaryTree<T> right)
{
element = obj;
if (left == null)
this.left = null;
else
this.left = left.getRootNode();
if (right == null)
this.right = null;
else
this.right = right.getRootNode();
}
/**
* Returns the number of non-null children of this node.
*
* @return the integer number of non-null children of this node
*/
public int numChildren()
{
int children = 0;
if (left != null)
children = 1 + left.numChildren();
if (right != null)
children = children + 1 + right.numChildren();
return children;
}
/**
* Return true if this node is a leaf and false otherwise.
*
* @return true if this node is a leaf and false otherwise
*/
public boolean isLeaf()
{
return (numChildren() == 0);
}
/**
* Return the element at this node.
*
* @return the element stored at this node
*/
public T getElement()
{
return element;
}
/**
* Return the right child of this node.
*
* @return the right child of this node
*/
public BinaryTreeNode<T> getRight()
{
return right;
}
/**
* Sets the right child of this node.
*
* @param node the right child of this node
*/
public void setRight(BinaryTreeNode<T> node)
{
right = node;
}
/**
* Return the left child of this node.
*
* @return the left child of the node
*/
public BinaryTreeNode<T> getLeft()
{
return left;
}
/**
* Sets the left child of this node.
*
* @param node the left child of this node
*/
public void setLeft(BinaryTreeNode<T> node)
{
left = node;
}
}
* Creates an empty binary search tree.
*/
public LinkedBinarySearchTree()
{
super();
}
/**
* Creates a binary search with the specified element as its root.
*
* @param element the element that will be the root of the new binary
* search tree
*/
public LinkedBinarySearchTree(T element)
{
super(element);
if (!(element instanceof Comparable))
throw new NonComparableElementException("LinkedBinarySearchTree");
}
/**
* Adds the specified object to the binary search tree in the
* appropriate position according to its natural order. Note that
* equal elements are added to the right.
*
* @param element the element to be added to the binary search tree
* @return
*/
public void addElement(T element, BinaryTreeNode node)
{
if (!(element instanceof Comparable))
throw new NonComparableElementException("LinkedBinarySearchTree");
Comparable<T> comparableElement = (Comparable<T>)element;
if (isEmpty())
root = new BinaryTreeNode<T>(element);
else
{
if (comparableElement.compareTo(root.getElement()) < 0)
{
if (root.getLeft() == null)
this.getRootNode().setLeft(new BinaryTreeNode<T>(element));
else
addElement(element, root.getLeft());
}
else
{
if (root.getRight() == null)
this.getRootNode().setRight(new BinaryTreeNode<T>(element));
else
addElement(element, root.getRight());
}
}
modCount++;
}
/**
* Adds the specified object to the binary search tree in the
* appropriate position according to its natural order. Note that
* equal elements are added to the right.
*
* @param element the element to be added to the binary search tree
*/
public LinkedBinarySearchTree(T element, BinaryTreeNode<T> node)
{
Comparable<T> comparableElement = (Comparable<T>)element;
if (comparableElement.compareTo(node.getElement()) < 0)
{
if (node.getLeft() == null)
node.setLeft(new BinaryTreeNode<T>(element));
else
addElement(element, node.getLeft());
}
else
{
if (node.getRight() == null)
node.setRight(new BinaryTreeNode<T>(element));
else
addElement(element, node.getRight());
}
}
【问题讨论】：
-
如果报错，怎么运行一次？
-
你能给出完整的堆栈跟踪吗？这将有助于调试问题
-
向我们展示
BinaryTreeNode构造函数和getElement()。 -
我编辑了代码以添加更多细节。