判断文件编码格式

	/**
     * 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(String fileName) throws Exception{
        BufferedInputStream bin = new BufferedInputStream(
        new FileInputStream(fileName));
        int p = (bin.read() << 8) + bin.read();
        String code = null;
        //其中的 0xefbb、0xfffe、0xfeff、0x5c75这些都是这个文件的前面两个字节的16进制数
        switch (p) {
            case 0xefbb:
                code = "UTF-8";
                break;
            case 0xfffe:
                code = "Unicode";
                break;
            case 0xfeff:
                code = "UTF-16BE";
                break;
            case 0x5c75:
            	code = "ANSI|ASCII" ;
            	break ;
            default:
                code = "GBK";
        }

        return code;
    }