À propos de Java sous Linux

How can I tell what version of Java I have installed?
https://askubuntu.com/questions/346608/how-to-make-firefox-use-the-newest-java-version-which-is-already-installed
https://askubuntu.com/questions/354361/how-to-install-the-java-plugin-for-firefox/354406
https://askubuntu.com/questions/901090/java-plugin-no-longer-supported-in-firefox-52-is-there-any-other-way-to-run-jav
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