One of the important aspects of being a software developer is to have a firm grasp and mastery of your chosen tool. Although many would consider that there may be better things to do like studying new tools related to the current project you’re handling which is necessary most of the time, studying and taking a certification for a legacy technology of your choice give you depth and solid fundamentals of programming. I, in particular have been aspiring to take Oracle 1Z0-808 exam which is for Java 8 Oracle Certified Associate (OCAJP). To learn more, here is a link of a recent passer of the exam. You may consider everything he/she has written if you want to take the same exam.
Software being 