I tried to get the path of main project set in Netbeans.
import org.netbeans.api.project.ui.OpenProjects;
import org.netbeans.api.project.Project;
import javax.tools.FileObject;
Project proj = OpenProjects.getDefault().getMainProject();
FileObject root = proj.getProjectDirectory();
String path = root.getPath();
When executing the following error is generated. i found than fileUtil is to be used instead of the above root.getpath().
Exception in thread "main" java.lang.NoClassDefFoundError: org/netbeans/modules/project/uiapi/Utilities
at org.netbeans.api.project.ui.OpenProjects.<init>(OpenProjects.java:88)
at org.netbeans.api.project.ui.OpenProjects.<clinit>(OpenProjects.java:83)