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
if (!isProjectInWorkspace(selectedProjects[i].getProjectName()))
				validProjects.add(selectedProjects[i]);
		}
		return (ProjectRecord[]) validProjects.toArray(new ProjectRecord[validProjects.size()]);
	}
	
	/**
	 * Determine if the project with the given name is in the current workspace.
	 * 
	 * @param projectName String the project name to check
	 * @return boolean true if the project with the given name is in this workspace
	 */
	private boolean isProjectInWorkspace(String projectName){
		if (projectName == null)
			return false;
		IProject[] workspaceProjects = getProjectsInWorkspace();
		for (int i = 0; i <workspaceProjects.length; i++){
			if (projectName.equals(workspaceProjects[i].getName()))
				return true;
		}
		return false;
	}
	
    /**
     *	Use the dialog store to restore widget values to the values that they held
     *	last time this wizard was used to completion.
     *	
     *	Method declared public only for use of tests.
     */	
    public void restoreWidgetValues() {