導出非公共類通過公共API

Question

我想跟隨在樹木教程：http://cslibrary.stanford.edu/110/BinaryTrees.html 這是迄今爲止我所編寫的代碼：

package trees.bst; 

import java.util.ArrayList; 
import java.util.List; 
import java.util.StringTokenizer; 

/** 
* 
* @author sachin 
*/ 
public class BinarySearchTree { 

    Node root = null; 

    class Node { 

     Node left = null; 
     Node right = null; 
     int data = 0; 

     public Node(int data) { 
      this.left = null; 
      this.right = null; 
      this.data = data; 
     } 
    } 

    public void insert(int data) { 
     root = insert(data, root); 
    } 

    public boolean lookup(int data) { 
     return lookup(data, root); 
    } 

    public void buildTree(int numNodes) { 
     for (int i = 0; i < numNodes; i++) { 
      int num = (int) (Math.random() * 10); 
      System.out.println("Inserting number:" + num); 
      insert(num); 
     } 
    } 

    public int size() { 
     return size(root); 
    } 

    public int maxDepth() { 
     return maxDepth(root); 
    } 

    public int minValue() { 
     return minValue(root); 
    } 

    public int maxValue() { 
     return maxValue(root); 
    } 

    public void printTree() { //inorder traversal 
     System.out.println("inorder traversal:"); 
     printTree(root); 
     System.out.println("\n--------------"); 
    } 

    public void printPostorder() { //inorder traversal 
     System.out.println("printPostorder traversal:"); 
     printPostorder(root); 
     System.out.println("\n--------------"); 
    } 

    public int buildTreeFromOutputString(String op) { 
     root = null; 
     int i = 0; 
     StringTokenizer st = new StringTokenizer(op); 
     while (st.hasMoreTokens()) { 
      String stNum = st.nextToken(); 
      int num = Integer.parseInt(stNum); 
      System.out.println("buildTreeFromOutputString: Inserting number:" + num); 
      insert(num); 
      i++; 
     } 
     return i; 
    } 

    public boolean hasPathSum(int pathsum) { 
     return hasPathSum(pathsum, root); 
    } 

    public void mirror() { 
     mirror(root); 
    } 

    public void doubleTree() { 
     doubleTree(root); 
    } 

    public boolean sameTree(BinarySearchTree bst) { //is this tree same as another given tree? 
     return sameTree(this.root, bst.getRoot()); 
    } 

    public void printPaths() { 
     if (root == null) { 
      System.out.println("print path sum: tree is empty"); 
     } 

     List pathSoFar = new ArrayList(); 
     printPaths(root, pathSoFar); 

    } 

    ///-------------------------------------------Public helper functions 
    public Node getRoot() { 
     return root; 
    } 
    //Exporting a non public Type through public API 
    ///-------------------------------------------Helper Functions 

    private boolean isLeaf(Node node) { 
     if (node == null) { 
      return false; 
     } 
     if (node.left == null && node.right == null) { 
      return true; 
     } 
     return false; 
    } 

    ///----------------------------------------------------------- 
    private boolean sameTree(Node n1, Node n2) { 
     if ((n1 == null && n2 == null)) { 
      return true; 
     } else { 
      if ((n1 == null || n2 == null)) { 
       return false; 
      } else { 
       if ((n1.data == n2.data)) { 
        return (sameTree(n1.left, n2.left) && sameTree(n1.right, n2.right)); 
       } 
      } 
     } 

     return false; 


    } 

    private void doubleTree(Node node) { 
     //create a copy 
     //bypass the copy to continue looping 
     if (node == null) { 
      return; 
     } 
     Node copyNode = new Node(node.data); 
     Node temp = node.left; 
     node.left = copyNode; 
     copyNode.left = temp; 
     doubleTree(copyNode.left); 
     doubleTree(node.right); 
    } 

    private void mirror(Node node) { 
     if (node == null) { 
      return; 
     } 
     Node temp = node.left; 
     node.left = node.right; 
     node.right = temp; 
     mirror(node.left); 
     mirror(node.right); 
    } 

    private void printPaths(Node node, List pathSoFar) { 
     if (node == null) { 
      return; 
     } 
     pathSoFar.add(node.data); 
     if (isLeaf(node)) { 
      System.out.println("path in tree:" + pathSoFar); 
      pathSoFar.remove(pathSoFar.lastIndexOf(node.data)); //only the current node, a node.data may be duplicated 
      return; 
     } else { 
      printPaths(node.left, pathSoFar); 
      printPaths(node.right, pathSoFar); 
     } 
    } 

    private boolean hasPathSum(int pathsum, Node node) { 
     if (node == null) { 
      return false; 
     } 
     int val = pathsum - node.data; 
     boolean ret = false; 
     if (val == 0 && isLeaf(node)) { 
      ret = true; 
     } else if (val == 0 && !isLeaf(node)) { 
      ret = false; 
     } else if (val != 0 && isLeaf(node)) { 
      ret = false; 
     } else if (val != 0 && !isLeaf(node)) { 
      //recurse further 
      ret = hasPathSum(val, node.left) || hasPathSum(val, node.right); 
     } 

     return ret; 

    } 

    private void printPostorder(Node node) { //inorder traversal 
     if (node == null) { 
      return; 
     } 
     printPostorder(node.left); 
     printPostorder(node.right); 
     System.out.print(" " + node.data); 

    } 

    private void printTree(Node node) { //inorder traversal 
     if (node == null) { 
      return; 
     } 
     printTree(node.left); 
     System.out.print(" " + node.data); 
     printTree(node.right); 
    } 

    private int minValue(Node node) { 
     if (node == null) { 
      //error case: this is not supported 
      return -1; 
     } 
     if (node.left == null) { 
      return node.data; 
     } else { 
      return minValue(node.left); 
     } 
    } 

    private int maxValue(Node node) { 
     if (node == null) { 
      //error case: this is not supported 
      return -1; 
     } 
     if (node.right == null) { 
      return node.data; 
     } else { 
      return maxValue(node.right); 
     } 
    } 

    private int maxDepth(Node node) { 
     if (node == null || (node.left == null && node.right == null)) { 
      return 0; 
     } 
     int ldepth = 1 + maxDepth(node.left); 
     int rdepth = 1 + maxDepth(node.right); 

     if (ldepth > rdepth) { 
      return ldepth; 
     } else { 
      return rdepth; 
     } 
    } 

    private int size(Node node) { 
     if (node == null) { 
      return 0; 
     } 
     return 1 + size(node.left) + size(node.right); 

    } 

    private Node insert(int data, Node node) { 
     if (node == null) { 
      node = new Node(data); 

     } else if (data <= node.data) { 
      node.left = insert(data, node.left); 
     } else { 
      node.right = insert(data, node.right); 
     } 
     //control should never reach here; 

     return node; 
    } 

    private boolean lookup(int data, Node node) { 
     if (node == null) { 
      return false; 
     } 
     if (node.data == data) { 
      return true; 
     } 
     if (data < node.data) { 
      return lookup(data, node.left); 
     } else { 
      return lookup(data, node.right); 
     } 
    } 

    public static void main(String[] args) { 
     BinarySearchTree bst = new BinarySearchTree(); 
     int treesize = 5; 
     bst.buildTree(treesize); 
     //treesize = bst.buildTreeFromOutputString("4 4 4 6 7"); 
     treesize = bst.buildTreeFromOutputString("3 4 6 3 6"); 
     //treesize = bst.buildTreeFromOutputString("10"); 
     for (int i = 0; i < treesize; i++) { 
      System.out.println("Searching:" + i + " found:" + bst.lookup(i)); 
     } 
     System.out.println("tree size:" + bst.size()); 
     System.out.println("maxDepth :" + bst.maxDepth()); 
     System.out.println("minvalue :" + bst.minValue()); 
     System.out.println("maxvalue :" + bst.maxValue()); 
     bst.printTree(); 
     bst.printPostorder(); 
     int pathSum = 10; 
     System.out.println("hasPathSum " + pathSum + ":" + bst.hasPathSum(pathSum)); 
     pathSum = 6; 
     System.out.println("hasPathSum " + pathSum + ":" + bst.hasPathSum(pathSum)); 
     pathSum = 19; 
     System.out.println("hasPathSum " + pathSum + ":" + bst.hasPathSum(pathSum)); 
     bst.printPaths(); 

     bst.printTree(); 
     //bst.mirror(); 
     System.out.println("Tree after mirror function:"); 
     bst.printTree(); 
     //bst.doubleTree(); 
     System.out.println("Tree after double function:"); 
     bst.printTree(); 
     System.out.println("tree size:" + bst.size()); 

     System.out.println("Same tree:" + bst.sameTree(bst)); 
     BinarySearchTree bst2 = new BinarySearchTree(); 
     bst2.buildTree(treesize); 
     treesize = bst2.buildTreeFromOutputString("3 4 6 3 6"); 
     bst2.printTree(); 
     System.out.println("Same tree:" + bst.sameTree(bst2)); 
     System.out.println("---"); 
    } 
} 

現在的問題是，NetBeans的顯示警告：導出非public類型通過公共API函數getRoot（）。 我寫這個函數來獲取樹的根用於sameTree（）函數，以幫助比較「this」與給定的樹。 也許這是一個OOP設計問題......我應該如何重構上面的代碼，我沒有得到這個警告，我在這裏失蹤的概念是什麼？

---

Answer 1

我真的不明白，爲什麼你甚至創造了getRoot（）方法。只要你在你的班級內，你甚至可以訪問同一班級的任何其他對象的私人領域。

所以，你可以改變

public boolean sameTree(BinarySearchTree bst) { //is this tree same as another given tree? 
    return sameTree(this.root, bst.getRoot()); 
} 

到

public boolean sameTree(BinarySearchTree bst) { //is this tree same as another given tree? 
    return sameTree(this.root, bst.root); 
} 

我還要補充一個 「短路徑」 爲您傳遞相同的情況下，以這種方式的情況下：

public boolean sameTree(BinarySearchTree bst) { //is this tree same as another given tree? 
    if (this == bst) { 
     return true; 
    } 
    return sameTree(this.root, bst.root); 
} 

Answer 2

的這裏的問題是，一些代碼可以稱之爲getRoot（），但將不能夠使用它的返回值，因爲你只給了Node類包訪問。

讓Node頂層類與它自己的文件，或至少把它公開