java判断文本文件编码格式

/**
	 * 判断文件的编码格式
	 * @param fileName :file
	 * @return 文件编码格式
	 * @throws Exception
	 */
	public static String codeString(File fileName) throws Exception{
		BufferedInputStream bin = new BufferedInputStream(
		new FileInputStream(fileName));
		int p = (bin.read() << 8) + bin.read();
		String code = null;
		
		switch (p) {
			case 0xefbb:
				code = "UTF-8";
				break;
			case 0xfffe:
				code = "Unicode";
				break;
			case 0xfeff:
				code = "UTF-16BE";
				break;
			default:
				code = "GBK";
		}
		IOUtils.closeQuietly(bin);
		return code;
	}