mvn package

Warning: JAVA_HOME environment variable is not set.
[INFO] Scanning for projects...
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[INFO] Building Mallet Topic-Modeling-Tool GUI 0.99-SNAPSHOT
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[INFO] --- maven-resources-plugin:2.6:copy-resources (copy-resources) @ TopicModelingTool ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
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[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ TopicModelingTool ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 4 resources
[INFO] 
[INFO] --- maven-compiler-plugin:2.5.1:compile (default-compile) @ TopicModelingTool ---
[INFO] Compiling 10 source files to /home/sigmund/Dropbox/ULB/phd/writing/git/topic-modeling-tool/TopicModelingTool/target/classes
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[INFO] BUILD FAILURE
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[INFO] Total time: 1.105s
[INFO] Finished at: Tue Mar 28 14:10:58 CEST 2017
[INFO] Final Memory: 7M/176M
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[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.5.1:compile (default-compile) on project TopicModelingTool: Fatal error compiling: tools.jar not found: /usr/lib/jvm/java-7-openjdk-amd64/jre/../lib/tools.jar -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException