Are there significant differences between, say, JDK 7 and JDK 11 (which latter I believe is the newest version of the JDK), where significance is defined by a change which might make someone who has learned an older version have Java lack knowledge or be only familiar with the old implementation of a feature? (Context: I want to learn Java but I don't know which version to start with - this is relevant because different resources teach different versions.)
closed as unclear what you're asking by gnat, Greg Burghardt, amon, Thomas Owens♦ Oct 19 '18 at 10:38
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The last 'major' release was Java 9.
Now, the schedule was changed for new releases every 6 months, but that doesn't mean a big change every new release.
That change on the calendar enabled more flexibility for developers that work on the updates in adding new features/or correcting bugs to the language without having to wait a long period of time. And if they were about to finish a feature but missed the window, they don't have to wait years to push that, because in 6 months a new version will be released.
As said on the comments by @Sikorski, the latest the better, but in Java 8 were added some really interesting features like lambdas, streams, a new date and time API, and a lot of more stuff. So probably Java 8 would be a good start.
Just showing how Java 8 would be a great start, on Oracle's certifications possibilities, the Java 8 is the last certification path available.