Bug 13034 Cannot create a Source Folder in a new Java Project
build 20020404 If you try and create a Source Folder in a Java Project you have just created you get an error preventing you from hitting finish. STEPS 1) Create Java Project Foo 2) Open New->Source Folder 3) Enter Bar as the name - you will get "Cannot nest entry Bar inside entry Foo/Bar" 4) Create a folder Bar. 5) Add it as a source folder in the Properties Dialog for Foo. No problem.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/BuildPathsBlock.java
public Control createControl(Composite parent) {
		fSWTWidget= parent;
		
		PixelConverter converter= new PixelConverter(parent);
		
		Composite composite= new Composite(parent, SWT.NONE);	
		
		GridLayout layout= new GridLayout();
		layout.marginWidth= 0;
		layout.numColumns= 1;		
		composite.setLayout(layout);
		
		TabFolder folder= new TabFolder(composite, SWT.NONE);
		folder.setLayout(new TabFolderLayout());	
		folder.setLayoutData(new GridData(GridData.FILL_BOTH));
		folder.addSelectionListener(new SelectionAdapter() {
			public void widgetSelected(SelectionEvent e) {
				tabChanged(e.item);
			}	
		});
		
		ImageRegistry imageRegistry= JavaPlugin.getDefault().getImageRegistry();
		
		TabItem item;
				
		fSourceContainerPage= new SourceContainerWorkbookPage(fWorkspaceRoot, fClassPathList, fBuildPathDialogField);		
		item= new TabItem(folder, SWT.NONE);
		item.setText(NewWizardMessages.getString("BuildPathsBlock.tab.source")); 
		item.setImage(imageRegistry.get(JavaPluginImages.IMG_OBJS_PACKFRAG_ROOT));
		item.setData(fSourceContainerPage);