Ensure java8 is installed instead of 9 (#3460)
Ensure java8 is installed instead of 9 (#3460)

Currently, java8 is no longer the default `current` version in brew cask.
Use `alternative` version for java8 now.

Signed-off-by: Tzu-Chiao Yeh <ca203f834d09a72ff2e02b86e00afea7d208a8ec@gmail.com>
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