system version: macos10.13.6-2018003 update
coexistence of jdk7 and jdk8 versions according to online configuration, alias command switching, I do not know whether it is successful
7 is still very different from 8, but the syntax of 7 can be run in 8. If there are no special requirements, just install 8. When writing code, be careful not to write a higher version of the syntax for the lower version to run. Jdk backward compatibility does very well.
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