首先遍歷來一下，這裏分為遞歸與不遞歸的兩種操作：

非遞歸操作

//非遞歸復用了 LinkedList
    private static void NotRecursive() {
        LinkedList<File> list=new LinkedList<>();
        int folderNum=0;
        int fileNum=0;
        
        File file=new File("E:/動腦");
        if(file.exists()){
            File[] fs=file.listFiles();
            
 
for(File f1:fs){
                if(f1.isDirectory()){
                    folderNum++;
                    list.add(f1);
//                    System.out.println("Folder Name:"+f1.getName());
                }else{
                    fileNum++;
                    System.out.println("File Name:"+f1.getName());
                }
            }
            File f2;
            
 
while(!list.isEmpty()){
                f2=list.removeFirst();
                fs=f2.listFiles();
                for(File f1:fs){
                    if(f1.isDirectory()){
                        folderNum++;
                        list.add(f1);
//                        System.out.println("Folder Name:"+f1.getName());
 

                    }else{
                        fileNum++;
                        System.out.println("File Name:"+f1.getName());
                    }
                }
            }
        }else{
            System.out.println("非文件目錄");
        }
        System.out.println("FileNum: "+fileNum+"   FolderNum: "+folderNum);
    }

遞歸操作：並篩選出MP3格式的文件

private static LinkedList<File> Recursive(String path) {
      
        LinkedList<File> list=new LinkedList<>();
        File file=new File(path);
        if(file.exists()){
            File[] fs =file.listFiles();
            for(File f1:fs){
                if(f1.isDirectory()){
                    Recursive(f1.getAbsolutePath());
                }else{
                    if(f1.getName().endsWith("mp3"))
                    list.add(f1);
                    System.out.println("File Name:"+f1.getName());
                }
            }
        }else{
            
        }
        return list;
    }

public class DirList {

    public static void main(String[] args) {
        String path="E:/動腦";
        File file=new File(path);
        String[] fs=file.list(new FilenameFilter() {
            private String tag=".mp3";
            @Override
            public boolean accept(File dir, String name) {
                return name.endsWith(tag);
            }
        });
        long l=0;
        Arrays.sort(fs);
        for(String s1:fs){
            System.out.println(s1);
            l+=new File("E:/動腦/"+s1).length();
        }
        
        System.out.println(l/1024/1024);
    }

}

File遍歷以及FilenameFilter的使用