Is it difficult to teach yourself Java? It should be difficult, right?
Why? The problem of self-control is that not everyone can sit and learn Java on that day. For example, in my class at that time, there were less than half of programmers (or computer majors) after graduation, so self-study might be more difficult.
Without the foundation of self-study, it is really hard to say how much you can learn. Everyone's progress and learning efficiency are different. It also depends on how long you spend learning Java every day. It is estimated that if you study more than 8 hours a day, you can reach the threshold of internship in 5 months. Learning Java from scratch is too much to learn.
So learning java depends on how you learn it. I suggest you train.