I am developing a cryptographic application using AES. I am using built-in libraries of java cryptography and it is working but

the problem is this that my program only encrypts .txt files and it doesn't encrypt/decrypt any other files. I've searched alot to find out a solution but it was all failure. So please anyone tell me How can I encrypt files of any type (and folders/directories) such as Office documents, Images, multimedia(audio/vedio) files etc.Kindly help me regarding this problem ASAP because I need to do it urgently. Any help would be greatly appreciated.

Thanks in advance.