private static void tree(File f,int level){
String preStr = ""; for (int i = 0; i < level; i++) { preStr+=" "; } File [] childs = f.listFiles(); for (int i = 0; i < childs.length; i++) { System.out.println(preStr+childs[i].getName()); if(childs[i].isDirectory()){ tree(childs[i],++level); } } }