Maven command to run a Java main class

There might be more than one Java classes in a Maven project that contains the main() function. To pick up a specific one to run, you can try the following command:

[sourcecode]
mvn exec:java -Dexec.mainClass="my_main_class_name"
[/sourcecode]

In case the memory is not enough, try the following command:

[sourcecode]
export MAVEN_OPTS=-Xmx1024m
[/sourcecode]
where 1024m is the max heap memory

Reimport Maven module in Intellij

I recently removed a Maven module from my Intellij project. Shortly after, I tried to reimport the same module again, but somehow Intellij stubbornly refuse to show it in the Project panel. Eventually I looked into the MyProject.ipr file and found the module’s pom.xml file appeared in the ignoreFiles list.

[sourcecode]
<option name="ignoredFiles">
<set>
<option value="/path/to/my/module/pom.xml" />
</set>
</option>
[/sourcecode]

After I deleted the specific line with the pom.xml, I was able to reimport the module successfully again.

Change Java environment in CentOS

See this blog

To install/ register a JVM use the following
/usr/sbin/alternatives --install "/usr/bin/java" "java" "/usr/java/default/bin/java" 2
/usr/sbin/alternatives --install "/usr/bin/javac" "javac" "/usr/java/default/bin/javac" 2

And to configure systemwide changes use
/usr/sbin/alternatives --configure java
/usr/sbin/alternatives --configure javac