code: public static boolean deleteDir(File dir) {
          if (null == dir || !dir.exists())
              return false;
          if (!dir.isDirectory())
              throw new RuntimeException("\"" + dir.getAbsolutePath() + "\" should be a directory!");
          File[] files = dir.listFiles();
          boolean re = false;
          if (null != files) {
              if (files.length == 0)
                  return dir.delete();
              for (File f : files) {
                  if (f.isDirectory())
                      re |= deleteDir(f);
                  else
                      re |= deleteFile(f);
              }
              re |= dir.delete();
          }
          return re;
      }
docs: 强行删除一个目录，包括这个目录下所有的子目录和文件
  
  @param dir
  目录
  @return 是否删除成功