Java、修改文件名

package pack1;

import java.io.File;
import java.security.SecureRandom;
import java.util.ArrayList;

public class ReviseFileName {
    public static void main(String[] args) {
        File rootDirectory = new File("D://srcRootDirectory");  //将在D盘创建一个名为srcRootDirectory的目录
        if (!rootDirectory.exists()) rootDirectory.mkdir();

        for (int i = 0; i < 10; i++)    //创建子目录
            createFile(rootDirectory, getRandomWords());

        ArrayList<String> list = new ArrayList<>();
        for (File file : rootDirectory.listFiles())
            list.add(file.getName());   //数组列表添加目录

        processFileName(list);  //处理目录名
        deleteDirectory(rootDirectory); //删除原目录

        rootDirectory = new File(rootDirectory.getAbsolutePath());
        if (!rootDirectory.exists()) rootDirectory.mkdir(); //重新创建原目录

        for (String s : list) //创建修改过的子目录
            createFile(rootDirectory, s);
    }

    //处理目录名
    public static void processFileName(ArrayList<String> list) {
        for (int i = 0; i < list.size(); i++) {
            int index = list.get(i).indexOf("_");   //获取符号"_"的下标
            String substring = list.get(i).substring(index + 1).trim(); //获取从下标开始的子串

            if (substring.length() == 1)    //如果子串的长度等于1，加0并在数组列表中重新设置
                list.set(i, list.get(i).substring(0, index + 1) + "0" + substring);
        }
    }

    //删除目录
    public static void deleteDirectory(File directory) {
        for (File file : directory.listFiles())
            file.delete();
        directory.delete();
    }

    //创建目录
    public static void createFile(File parentFile, String name) {
        File file = new File(parentFile, name);
        if (!file.exists()) file.mkdir();
    }

    //返回随机目录名
    public static String getRandomWords() {
        return "Exercise" + getRandomNumber() + "_" + getRandomNumber();
    }

    //返回1~20的随机数
    public static int getRandomNumber() {
        return 1 + new SecureRandom().nextInt(20);
    }
}