列出文件夹下的文件，递归和非递归实现

package com.robert;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

public class Main3 {
    public static void main(String args[]) {
        File file = new File("/Users/robert/Downloads/资料/");
        try {
            StringBuffer stringBuffer = new StringBuffer();
            printFilePath(file, stringBuffer);
            File logFile = new File("/Users/robert/Documents/log.txt");
            logFile.delete();
            FileWriter fileWriter = new FileWriter(logFile, true);
            fileWriter.write(stringBuffer.toString());
            fileWriter.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void printFilePath(File file, StringBuffer stringBuffer) throws IOException {
        if (!file.exists()) {
            throw new RuntimeException("file is not exist");
        }

        if (file.isDirectory()) {
            File[] files = file.listFiles();
            for (File tempFile : files) {
                printFilePath(tempFile, stringBuffer);
            }
        } else {
            stringBuffer.append(file.getAbsolutePath()).append("\n");
        }
    }

    public static void printFilePath2(File file) throws IOException {
        if (!file.exists()) {
            throw new RuntimeException("file is not exist");
        }
        File logFile = new File("/Users/robert/Documents/log2.txt");
        logFile.delete();
        FileWriter fileWriter = new FileWriter(logFile, true);
        List files = new LinkedList<>();
        if (file.isDirectory()) {
            Collections.addAll(files, file.listFiles());
        } else {
            // System.out.println(file.getAbsolutePath());
            fileWriter.write(file.getAbsolutePath());
        }

        while (files.size() > 0) {
            File tempFile = files.get(0);
            files.remove(tempFile);
            if (tempFile.isDirectory()) {
                Collections.addAll(files, tempFile.listFiles());
            } else {
                // System.out.println(tempFile.getAbsolutePath());
                fileWriter.write(tempFile.getAbsolutePath());
                fileWriter.write("\n");
            }
        }
        fileWriter.close();

    }
}