Eclipse: Change general to Java project

You have a Eclipse project, which contains Java code - but you didn't set it up as a Java project when you created or checked out this project. So since Eclipse doesn't allow you to change the project type inside the Gui, you are stucked.

Solution: add the java nature

Open the .project file and add java nature and builders.

<projectDescription>
<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
<natures>
<nature>org.eclipse.jdt.core.javanature</nature>
</natures>
</projectDescription>
And in .classpath, reference the Java libs:

<classpath>
<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
</classpath>