This is probably a common thread asking where to start in getting the proper training materials to got for the Java 8 certs. However, I want to point out an interesting perspective (maybe more common than I think).
I have about 8 years give or take of java development experience (almost 12 years total in some aspect of software engineering (I did some C programming for awhile, DevOps most recently for a few years). You would think that would lead to you to be well positioned to be an attractive candidate. However, I'm sure I have left a couple of interviewers disappointed thinking they had their guy before interviewing me.
I was pretty much self taught (and I think that is largely the problem) and actually have a business degree not CS or something related. Note in college I did take a couple java classes and a C++ class, that was more or less how I was able to get an entry level software dev job to begin with. Despite the fact I have a pretty good knowledge of OOP and concepts and know I could develop pretty much any Java app someone asked me to. My "off the top of my head" knowledge is severely lacking. This has been exposed by recently starting to explore other opportunities and despite my interview prep, being stumped by some of the questions posed to me. I think the age of the internet has been helpful in obtaining answers for programming questions in a timely manner, but is not very useful in retaining the knowledge in your head. When you know you can just bookmark a programming solution or record it in a cheat sheet, your brain tends to treat it as something you don't need to know.
For reference I've taken a number of mock certification exams to try and gauge where I am, my average scores are around 50%, knowing I was still guessing on some of the answers I got right.
Just curious where you think the right place for me to start would be.