PHP took me a couple of weeks before I considered myself good enough at it, perl took me a week before I felt confident that I knew enough of it, Python took a couple of months before I could say I had a decent grasp on the language. Java I've been using for over 5 years, took me over a year before I felt I had it under control.
The Java ecosystem is huge and is growing at an enormous pace and the Java language itself is only one JVM language out of many other (including Groovy, Kotlin, Scala, Clojure, Ceylon, Jruby, Jython, etc etc). The Java language itself is also hard to master - so many things to learn!
Just keep at it and study all the things, mastering at least one JVM language will open many doors for you and make you a better programmer in the long-run.