Encode and decoder

Please see the files attached for description and requirements of project! I will also send what I have done so far re project. I have a good bit of the project completed I just need some finishing touches with improving efficiency and running time. I will also need UML Diagram of the finished code to be created. that the API is as efficient as possible I need it to be completed between 7pm-9.30pm (european time) on the 20th of April. I need the running time to be commented where applicable, documented using JavaDocs to be tested with 100% coverage Should not take that much time. I am willing to negotiate cost.