Bug 80833 [Import/Export] Import exisiting should pre-check for project already in workspace
While it is good that it lets you import projects in the default workspace location, it should not let you select projects that already exist in the workspace (since importing such a project will fail). When searching for .project files in the file system, it could use IWorkspaceRoot.findFilesForLocation followed by checking IFile.exists() to filter out .project files for existing projects.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/WizardProjectsImportPage.java
optionsGroup.setLayout(new GridLayout());
		optionsGroup.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
		
		copyCheckbox = new Button(optionsGroup, SWT.CHECK);
		copyCheckbox.setText(DataTransferMessages.WizardProjectsImportPage_CopyProjectsIntoWorkspace);
		copyCheckbox.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
		copyCheckbox.addSelectionListener(new SelectionAdapter(){
			public void widgetSelected(SelectionEvent e) {
				copyFiles = copyCheckbox.getSelection();
			}
		});
	}
	/**
	 * Create the checkbox list for the found projects.
	 * 
	 * @param workArea
	 */
	private void createProjectsList(Composite workArea) {
		Label title = new Label(workArea, SWT.NONE);
		title
				.setText(DataTransferMessages.WizardProjectsImportPage_ProjectsListTitle);
		Composite listComposite = new Composite(workArea, SWT.NONE);
		GridLayout layout = new GridLayout();
		layout.numColumns = 2;
		layout.marginWidth = 0;
		layout.makeColumnsEqualWidth = false;
		listComposite.setLayout(layout);
		listComposite.setLayoutData(new GridData(GridData.GRAB_HORIZONTAL
				| GridData.GRAB_VERTICAL | GridData.FILL_BOTH));
		projectsList = new CheckboxTreeViewer(listComposite, SWT.BORDER);