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java - 将 void 返回到文本文件的打印方法

问题描述

问这个问题我感觉像个菜鸟，但是在我当前的驱动程序中，我已经使用迭代器成功地将树的预排序打印到文本文件中。我不知道如何打印我的递归方法，因为我不能将它们放入 println 语句中，因为它们是无效方法。我知道我应该让该方法将编写器作为参数，但不知道该怎么做（驱动程序的最后几个 println 语句）。任何帮助表示赞赏！

司机：

package driver;

import java.io.*;
import java.util.*;

public class Driver {
    
    private static Scanner file;
    static PrintWriter outputFilePrinter;
    static Scanner inputFileScanner;

    public static void main(String[] args) throws FileNotFoundException {
       
        Scanner inFile; //Declaring scanner obj
        PrintWriter printWriter = new PrintWriter("output.txt"); //Text file where results are printed to
        inFile = new Scanner(new File("input.txt")); //Text file where student names and associated number are read from
        
        BinarySearchTreeInterface<String> aTree = new BinarySearchTree<>() {}; //Giving access to BinarySearchTree methods
      
        
        while (inFile.hasNext()) { //Scans input file
            String name = inFile.nextLine(); //Assigns contents to string obj
            aTree.add(name); //Add string to a tree
        } //End while
        
    
        Iterator<String> traverse = aTree.getPreorderIterator(); //Using iterator to print tree in an "postorder" fashion   
            while (traverse.hasNext())
        printWriter.println(traverse.next()); //Prints tree
        
        System.out.println("Postorder Recrusive: ");
        aTree.postorderTraverse();
        System.out.println("");
        System.out.println("Inorder Recursive: ");
        aTree.inorderTraverse();
     
        printWriter.close(); //Closes file
       
    } //End Main

} //End Driver

我试图打印的递归方法：

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

    public void inorderTraverse(BinaryNode<T> node) {
        if (node != null) {
            inorderTraverse(node.getLeftChild());
            System.out.println(node.getData());
            inorderTraverse(node.getRightChild());
        }
    }

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

    public void postorderTraverse(BinaryNode<T> node) {
        if (node != null) {  
        postorderTraverse(node.getLeftChild());
        postorderTraverse(node.getRightChild());
        System.out.println(node.getData());
        }
    }

标签： javatree

解决方案

您可以将遍历代码更改为

public void inorderTraverse(PrintWriter printWriter) {
    inorderTraverse(root, printWriter);
}

public void inorderTraverse(BinaryNode<T> node, PrintWriter printWriter) {
    if (node != null) {
        inorderTraverse(node.getLeftChild(), printWriter);
        printWriter.println(node.getData());
        inorderTraverse(node.getRightChild(), printWriter);
    }
}

public void postorderTraverse(PrintWriter printWriter) {
    postorderTraverse(root, printWriter);
}

public void postorderTraverse(BinaryNode<T> node, PrintWriter printWriter) {
    if (node != null) {  
        postorderTraverse(node.getLeftChild(), printWriter);
        postorderTraverse(node.getRightChild(), printWriter);
        printWriter.println(node.getData());
    }
}

甚至

public void inorderTraverse(Consumer<T> consumer) {
    inorderTraverse(root, consumer);
}

public void inorderTraverse(BinaryNode<T> node, Consumer<T> consumer) {
    if (node != null) {
        inorderTraverse(node.getLeftChild(), consumer);
        consumer.accept(node.getData());
        inorderTraverse(node.getRightChild(), consumer);
    }
}

public void postorderTraverse(Consumer<T> consumer) {
    postorderTraverse(root, consumer);
}

public void postorderTraverse(BinaryNode<T> node, Consumer<T> consumer) {
    if (node != null) {  
        postorderTraverse(node.getLeftChild(), consumer);
        postorderTraverse(node.getRightChild(), consumer);
        consumer.accept(node.getData());
    }
}

并像这样调用第二个变体：

aTree.postorderTraverse(printWriter::println);
aTree.postorderTraverse(System.out::println);

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