import java.io.File;
import java.io.FileFilter;

public class PrintDir {
    public static void main(String[] args) {

        File dir = new File("/");
        File[] files = null;

        FileFilter fileFilter = new FileFilter() {
            @Override
            public boolean accept(File pathname) {
                return pathname.isDirectory();
            }
        };

        files=dir.listFiles(fileFilter);
        System.out.println(files.length);
        if (files.length ==0){
            System.out.println("目录为空！！");
        }else {
            for (int i=0; i<files.length; i++){
                File filename = files[i];
                System.out.println(filename.toString());
            }
        }
    }
}