Bug 52064 Content assist in "New Class" Dialog shows interfaces
Content Assist is available for the superclass in M7. However it also lists interfaces. If an interface is selected, the generated class "extends" it instead of "implementing" it.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/wizards/NewTypeWizardPage.java
private ImportsStructure fImportsStructure;
		private HashSet fAddedTypes;
		
		 ImportsManager(IImportsStructure importsStructure) {
			fImportsStructure= (ImportsStructure) importsStructure;
		}
		 ImportsManager(ICompilationUnit createdWorkingCopy) throws CoreException {
			IPreferenceStore store= PreferenceConstants.getPreferenceStore();
			String[] prefOrder= JavaPreferencesSettings.getImportOrderPreference(store);
			int threshold= JavaPreferencesSettings.getImportNumberThreshold(store);			
			fAddedTypes= new HashSet();
			
			fImportsStructure= new ImportsStructure(createdWorkingCopy, prefOrder, threshold, true);
		}
		 ImportsStructure getImportsStructure() {
			return fImportsStructure;
		}
				
		/**
		 * Adds a new import declaration that is sorted in the existing imports.
		 * If an import already exists or the import would conflict with another import
		 * of an other type with the same simple name  the import is not added.
		 * 
		 * @param qualifiedTypeName The fully qualified name of the type to import
		 * (dot separated)
		 * @return Returns the simple type name that can be used in the code or the
		 * fully qualified type name if an import conflict prevented the import
		 */				
		public String addImport(String qualifiedTypeName) {
			fAddedTypes.add(qualifiedTypeName);