我想问这个问题，但在我目前的驱动程序，我已经打印出了一个使用迭代器到文本文件的树的前序成功。我不知道如何打印我的递归方法，因为我不能把它们放到println语句中，因为它们是void方法。我知道我应该让这个方法把writer作为一个参数，但不知道怎么做（driver的最后几个println语句）。感谢您的帮助！
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

我正在尝试打印的递归方法：

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());
        }
    }