I know that the "Unsupported major.minor version 52.0" Error points to the fact that the java code was compiled with Java 8 and it was attempted to execute it with an earlier version.
I know that it is therefore suggested to have JAVA_HOME and PATH point to the correct version of Java.
From all that I can tell I have my system already pointing to the correct version:
me@computer ~ $ java -version
java version "1.8.0_102"
Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)
me@computer ~ $ which java
/home/me/bin/jdk1.8.0_102_64bit/bin/java
me@computer ~ $ echo $JAVA_HOME
/home/me/bin/jdk1.8.0_102_64bit
However, I still get the below error when trying to execute elasticsearch (installed via apt-get):
me@computer ~ $ sudo -i service elasticsearch start
* Starting Elasticsearch Server
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/elasticsearch/bootstrap/Elasticsearch : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
...
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
Edit:
The PATH variable (in constrast to other variables like JAVA_HOME) is reset with sudo on ubuntu-based linuxes, one suggested solution is to set the variable again using sudo env
:
me@computer ~ $ sudo echo $JAVA_HOME
/home/me/bin/jdk1.8.0_102_64bit
me@computer ~ $ sudo java -version
java version "1.7.0_121"
OpenJDK Runtime Environment (IcedTea 2.6.8) (7u121-2.6.8-1ubuntu0.14.04.1)
OpenJDK 64-Bit Server VM (build 24.121-b00, mixed mode)
me@computer ~ $ sudo env PATH=$PATH java -version
java version "1.8.0_102"
Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)
However, this does not work for my actual problem (starting Elasticsearch):
me@computer ~ $ sudo env PATH=$PATH service elasticsearch start
* Starting Elasticsearch Server
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/elasticsearch/bootstrap/Elasticsearch : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
...