As a senior member of my organization, I have to take interviews on regular basis as part of the recruitment process of our company. As an interviewer, I have witnessed some interesting observations about Java and the knowledge of individual interviewees. The experience ranges of the interviewees vary from around three to eight years.
In many cases, my observation is that the candidate knows the topic very well. Their theoretical knowledge is very good. And their answer quality shows that they have had hands-on work experience in different areas of core Java, like exception handling, the collections framework, generics, and objects. They have a more or less clear idea of what those things are. And in many cases, they are aware of new features added in more recent versions.