Question

我正在制作一个程序，该程序能够按升序或降序对整数或分数列表进行排序。我使用的是GUI，当我按下按钮时，原始列表应添加到二叉树中。应该执行有序遍历，并且该列表应显示在GUI中。我已经完成了所有工作，但是随后我发现我应该使搜索树类具有通用性。我已将类更改为通用类，但在从GUI调用该类以实际执行遍历时遇到问题。您能提供的任何帮助将不胜感激。

这是带有Node类的原始SearchTree

public class SearchTree {


// creates the root of the tree
Node root;

// String to store the answer while tree is being traversed
private String answer = "";

SearchTree (Object x) {

    root = new Node(x);
}

/* recursive method adding integers to the tree,
 * placing it depending on if it is smaller or larger
 * than the parent node
 */ 
Node insertInteger(Node node, Integer x) {
    if (node == null) {
        return node = new Node(x);
    }
    if (x < (Integer) node.parent) {
        node.left = insertInteger(node.left, x);
    } else {
        node.right = insertInteger(node.right, x);
    }
    return node;
}

// recursive method for adding fractions to the tree
Node insertFraction(Node node, Fraction x) {
    if (node == null) {
        return node = new Node(x);
    }
    if (x.compareTo((Fraction) node.parent) < 1) {
        node.left = insertFraction(node.left, x);
    }else {
        node.right = insertFraction(node.right, x);
    }
    return node;
}

// in order traversal for the ascending order
String inOrder(Node node) {
    if (node != null) {
        inOrder(node.left);
        answer = answer + node.parent + " ";
        inOrder(node.right);
    }
    return answer;
}

// reversed traversal for the descending order
String descendingOrder(Node node) {
    if (node != null) {
        descendingOrder(node.right);
        answer = answer + node.parent + " ";
        descendingOrder(node.left);
    }
    return answer;
 }
}

class Node {

 Object parent;
 Node left;
 Node right;

 // Constructors
 Node(Object theParent) {
    this(theParent, null, null);
 }

 private Node(Object theParent, Node lChild, Node rChild) {
    parent = theParent;
    this.left = lChild;
    this.right = rChild;
 }
}

通用SearchTree

public class SearchTree<T extends Comparable<T>> {

Node root;  //root node of the tree

 //defines each node of tree
class Node{
    T value;  
    Node right,left;  

    Node(T value){
        this.value = value;
    }
}

// inserts new node in tree
public void insert(T value){
    if(isEmpty())
        root = new Node(value);  
    else
        insert(root, value);  
}

 // insert nodes in there proper places
private void insert(Node node, T value){
    if(value.compareTo(node.value) < 0){  //if new value less than parent node
        if(node.left == null)  //if left null then add
            node.left = new Node(value);
        else
            insert(node.left,value);  //if left not null then recursive call
    }
    else if(value.compareTo(node.value) >= 0){  //if new value same or greater than parent node
        if(node.right == null)  //if right null then add
            node.right = new Node(value);
        else
            insert(node.right,value);  //if right not null then recursive call
    }
}

// returns root value
public T peek(){
    return root.value;
}

// makes sure tree is not empty
public boolean isEmpty(){
    return (root == null)? true : false;
}

}

这是问题

private <T extends Comparable<T>> void intOperation() throws NumberFormatException {

        try {
            String[] stringArray = txtOrig.getText().split(" ");
            int [] intArray = new int[stringArray.length];
            for (int i = 0; i < stringArray.length; i++) {
                intArray[i] = Integer.parseInt(stringArray[i]);
            }

            SearchTree<T> st = new SearchTree<T>();
            for (int i = 1; i < intArray.length; i++) {
                T val = intArray[i];
                st.insert(st.root, val);
            }

            if (rdbtnAscend.isSelected()) {
                txtSort.setText(st.inOrder(st.root));
            }else {
                txtSort.setText(st.descendingOrder(st.root));
            }

  /***** This is the original along with the first bracketed try block

            SearchTree st = new SearchTree(intArray[0]);
            for (int i = 1; i < intArray.length; i++) {
                st.insertInteger(st.root, intArray[i]);
            }

            if (rdbtnAscend.isSelected()) {
                txtSort.setText(st.inOrder(st.root));
            }else {
                txtSort.setText(st.descendingOrder(st.root));
            }
  */

这是我被卡住的原因。如何从该try块调用通用SearchTree类？

Answer 1

您正在使用占位符类型T正确声明您的类。实例化类时，您使用的是占位符，而不是您希望通用类为的类型。

SearchTree<Integer> st = new SearchTree<Integer>();

通用类将需要使用具体类型实例化，以使所有类型检查正常工作。

如何从另一个类中引用一个通用类

1 个答案: