Bug 18132 New wizards should verify if folder is on classpath
1. create J project 'P' with source folder setup (source folder 'src') 2. use new wizard to create a class ==> you can create a class inside 'P' or in a folder which is not on the classpath
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/wizards/NewContainerWizardPage.java
private IPackageFragmentRoot chooseSourceContainer(IJavaElement initElement) {
		Class[] acceptedClasses= new Class[] { IPackageFragmentRoot.class, IJavaProject.class };
		TypedElementSelectionValidator validator= new TypedElementSelectionValidator(acceptedClasses, false) {
			public boolean isSelectedValid(Object element) {
				try {
					if (element instanceof IJavaProject) {
						IJavaProject jproject= (IJavaProject)element;
						IPath path= jproject.getProject().getFullPath();
						return (jproject.findPackageFragmentRoot(path) != null);
					} else if (element instanceof IPackageFragmentRoot) {
						return (((IPackageFragmentRoot)element).getKind() == IPackageFragmentRoot.K_SOURCE);
					}
					return true;
				} catch (JavaModelException e) {
					JavaPlugin.log(e.getStatus()); 
				}
				return false;
			}
		};
		
		acceptedClasses= new Class[] { IJavaModel.class, IPackageFragmentRoot.class, IJavaProject.class };
		ViewerFilter filter= new TypedViewerFilter(acceptedClasses) {
			public boolean select(Viewer viewer, Object parent, Object element) {
				if (element instanceof IPackageFragmentRoot) {
					try {
						return (((IPackageFragmentRoot)element).getKind() == IPackageFragmentRoot.K_SOURCE);
					} catch (JavaModelException e) {
						JavaPlugin.log(e.getStatus()); 
						return false;