Maybe you're asking the candidates boring questions?. Try asking them moderately probing, but non-boring questions like:

  "What made you want to go into software development?"
  "If you weren't a developer, what other job would you want to do?"
  "What features do you especially like about Java?"
  "What was an interesting problem that you've solved?"
  "What was the most challenging bug that you've fixed?"
  "Why do you want to work here, as opposed to some other place?"
  "If you could change the Java language, what would you change about it?"