Programmers are responsible for developing code to build products. In an interview context, expect to be quizzed on your technical skills through different kinds of computing problems or brainteasers. The specific questions you are asked will depend on what type of programming position you are looking for. Try researching a specific discipline such as web development, application development, or system development.
There are no truly difficult questions, unless you are interviewing directly for a programming position, then you had better know the language you are interviewing.
For Java you can just use a website that has java interview questions for practice.
can you tell me which website to practice?