二叉搜索树findNode方法总是返回根

Question

我有一个整数的二叉搜索树，包括1、2、...、9。我的遍历方法工作，我知道节点在那里，并且以正确的顺序。

 //this method calls findNode(int,BSTNode) and prints a message if the value is found
// in the tree
public void searchPrint(int value)
{
    System.out.print(value);
    if (findNode(value, root) == null)
    {
        System.out.println(" does not exist in the tree.");
    } else
    {
        System.out.println(" exists in the tree.");
    }
}//end searchPrint(int) ----------------------------------------------------

//this method recursively looks for the node that contains 'value' and 
//returns that node if it is found.  Returns null if no nodes contain
//the value.
private BSTNode findNode(int value, BSTNode current)
{
    if(current != null)
    {
        if (value == current.getValue())
        {
            System.out.print("  **Test* entering "
                    + "if(value = current.value loop...**  ");

            return current;
        } else 
        {
            if (value < current.getValue())
            {
                findNode(value,current.getLeft());
            } else 
            {
                findNode(value,current.getRight());
            }
        }
    } else
    {
        return null;
    }
    return current;
}//end findNode(int,BSTNode) -----------------------------------------------

    Traversals:

in-order
1
2
3
4
5
6
7
8
9
pre-order
6
2
1
4
3
5
7
9
8
post-order
1
3
5
4
2
8
9
7
6
7  **Test* entering if(value = current.value loop...**   exists in the tree.
5  **Test* entering if(value = current.value loop...**   exists in the tree.
6  **Test* entering if(value = current.value loop...**   exists in the tree.
1  **Test* entering if(value = current.value loop...**   exists in the tree.
12 exists in the tree.
15 exists in the tree.

我在纸上写下了当我搜索一个值时发生的事情，它返回根是没有意义的。我做错了什么？

Answer 1

在对findNode（）的递归调用中缺少return，所以它总是在方法的末尾到达return

更改为：

private BSTNode findNode(int value, BSTNode current)
{
    if(current != null)
    {
        if (value == current.getValue())
        {
            System.out.print("  **Test* entering "
                    + "if(value = current.value loop...**  ");

            return current;
        } else 
        {
            if (value < current.getValue())
            {
                return findNode(value,current.getLeft());
            } else 
            {
                return findNode(value,current.getRight());
            }
        }
    } else
    {
        return null;
    }
    return current;
}