code: public static File createTmpDir(String folderName)
  	{
  		File temp = new File(System.getProperty("java.io.tmpdir"), folderName);
  		if (!temp.exists()) {
  			temp.mkdirs();
  			temp.deleteOnExit();
  		}
  		return temp;
  	}
docs: 创建系统临时目录并在jvm关闭后自动删除
  @param folderName
  @return