java修改当前目录和目录以下所有文件夹中的jpg图片、mp3音频文件的后缀名

import java.io.File;
import java.util.Scanner;

public class test2pro { 
    public static void main(String[] args) { 
        Scanner sc = new Scanner(System.in);
        System.out.println("please choose whether to modify or recover?");
        String choose = sc.nextLine();
        int flag = 0;
        if(choose.equals("modify")){ 
            flag =1;

        }else{ 
            flag = 0;
        }
        modifyExtension(System.getProperty("user.dir"),flag);

        System.out.println("done");
    }
    //when flag = 1, change the extension ;
    //when flag =0 , just recover it;
    public static void modifyExtension(String path,int num) { 
        File f = new File(path);
        File[] fs = f.listFiles();
        for (File subFile : fs) { 
            if (subFile.isDirectory()){ 
                modifyExtension(subFile.getPath(),num);
            } else { 
                String name = subFile.getName();
                int len = name.length()-3;
                if(num>0){ 
                    if (name.endsWith("jpg")) { 
                        modifyExtension(subFile,"ide",len,name);
                    }
                    if (name.endsWith("mp3")) { 
                        modifyExtension(subFile,"vid",len,name);
                    }
                }else{ 
                    if (name.endsWith("ide")) { 
                        modifyExtension(subFile,"jpg",len,name);
                    }
                    if (name.endsWith("vid")) { 
                        modifyExtension(subFile,"mp3",len,name);
                    }
                }
                
            }
        }
    }

    public static void modifyExtension(File f,String finalExtensionName,int len,String name){ 
        f.renameTo(new File(f.getParent() + "/" + name.substring(0, len) + finalExtensionName));
    } 

}