common_helper/src/main/java/com/xiongyingqi/util/FileType.java
private static String bytesToHexString(byte[] src){
        StringBuilder stringBuilder = new StringBuilder();
        if(null==src || src.length <= 0){
            return null;
        }
        for(int i = 0; i < src.length; i++){
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if(hv.length() < 2){
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }
private static String bytesToHexString(byte[] src){
        StringBuilder stringBuilder = new StringBuilder();
        if(null==src || src.length <= 0){
            return null;
        }
        for(int i = 0; i < src.length; i++){
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if(hv.length() < 2){
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }
得到上传文件的文件头
@param src
@return