Convert eclipse project to java project

Open .project file located in the project root folder and following lines;

<buildSpec>
<buildCommand>
<name>org.eclipse.jdt.core.javabuilder</name>
<arguments>
</arguments>
</buildCommand>
</buildSpec>
<natures>
<nature>org.eclipse.jdt.core.javanature</nature>
</natures>

Save it and refresh the project in eclipse. That's about it.