idem, j'ai réinstallé sans succès, testé avec plusieurs versions... toujours le même message d'erreur
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
Erreur : impossible de trouver ou charger la classe principale net.minecraft.client.main.Main
log
[22:11:49 INFO]: Minecraft Launcher 1.6.82-j (through bootstrap 5) started on linux...
[22:11:49 INFO]: Current time is Oct 25, 2017 10:11:49 PM
[22:11:49 INFO]: System.getProperty('os.name') == 'Linux'
[22:11:49 INFO]: System.getProperty('os.version') == '4.4.0-97-generic'
[22:11:49 INFO]: System.getProperty('os.arch') == 'amd64'
[22:11:49 INFO]: System.getProperty('java.version') == '1.8.0_112'
[22:11:49 INFO]: System.getProperty('java.vendor') == 'Oracle Corporation'
[22:11:49 INFO]: System.getProperty('sun.arch.data.model') == '64'
[22:11:49 INFO]: proxy == DIRECT
[22:11:49 INFO]: JFX is already initialized
[22:11:50 INFO]: Refreshing local version list...
[22:11:50 INFO]: Refreshing remote version list...
[22:11:50 INFO]: Refresh complete.
[22:11:50 INFO]: Loaded 2 profile(s); selected 'EstCar'
[22:11:50 INFO]: Refreshing auth...
[22:11:50 INFO]: Logging in with access token
[22:11:55 INFO]: Getting syncinfo for selected version
[22:11:55 INFO]: Queueing library & version downloads
...
[22:11:56 INFO]: Job 'Version & Libraries' finished successfully (took 0:00:00.398)
[22:11:56 INFO]: Launching game
[22:11:56 INFO]: Unpacking natives to /home/david/.minecraft/versions/1.12.2/1.12.2-natives-11074828282756
[22:11:56 INFO]: Launching in /home/david/.minecraft
[22:11:56 INFO]: Half command: /usr/lib/jvm/oracle-java8-jre-amd64/bin/java -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M net.minecraft.client.main.Main
[22:11:56 INFO]: Looking for orphaned versions to clean up...
[22:11:56 INFO]: Looking for old natives & assets to clean up...
[22:11:56 ERROR]: Game ended with bad state (exit code 1)
[22:11:56 INFO]: Ignoring visibility rule and showing launcher due to a game crash
[22:11:56 INFO]: Deleting /home/david/.minecraft/versions/1.12.2/1.12.2-natives-11074828282756
