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
public void changeControlPressed(DialogField field) {
			containerChangeControlPressed(field);
		}
		
		
		public void dialogFieldChanged(DialogField field) {
			containerDialogFieldChanged(field);
		}
	}
	
	private void containerChangeControlPressed(DialogField field) {
		
		IPackageFragmentRoot root= getPackageFragmentRoot();
		root= chooseSourceContainer(root);
		if (root != null) {
			setPackageFragmentRoot(root, true);
		}
	}
	
	private void containerDialogFieldChanged(DialogField field) {
		if (field == fContainerDialogField) {
			fContainerStatus= containerChanged();