1.UUID

	/**
	 * 生成唯一的檔名:
	 */
	public static String getUUIDFileName(String fileName){
		// 將檔名的前面部分進行擷取：xx.jpg   --->   .jpg
		int idx = fileName.lastIndexOf(".");
		String extention = fileName.substring(idx);
		String uuidFileName = UUID.randomUUID().toString().replace("-", "")+extention;
		return uuidFileName;
	}
	
	public static void main(String[] args) {
		System.out.println(getUUIDFileName("1.jpg"));
	}
 

2.時間戳

String fileName = System.currentTimeMillis() + "_" + imgFile.getOriginalFilename();