如何用Java实现列出某个目录下的所有子目录？

public static void main(String[] args) throws Exception
{
       getFile(new File(“C:entityBean”),”t”);
}
public static void getFile(File f,String sem) throws Exception
{
        System.out.println(sem+f.getName());
        File fl[]=f.listFiles();
        if(fl.length>=1)
        {
            for(int i=0;i<fl.length;i++)
            {
                if(fl[i].isDirectory())
                {
                    getFile(fl[i],sem+”t”);
                }
            }
        }
    }