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
protected IStatus superClassChanged() {
		StatusInfo status= new StatusInfo();
		IPackageFragmentRoot root= getPackageFragmentRoot();
		fSuperClassDialogField.enableButton(root != null);
		
		fSuperClass= null;
		
		String sclassName= getSuperClass();
		if (sclassName.length() == 0) {
			
			return status;
		}
		IStatus val= JavaConventions.validateJavaTypeName(sclassName);
		if (val.getSeverity() == IStatus.ERROR) {
			status.setError(NewWizardMessages.getString("NewTypeWizardPage.error.InvalidSuperClassName")); 
			return status;
		} 
		if (root != null) {
			try {		
				IType type= resolveSuperTypeName(root.getJavaProject(), sclassName);
				if (type == null) {
					status.setWarning(NewWizardMessages.getString("NewTypeWizardPage.warning.SuperClassNotExists")); 
					return status;
				} else {
					if (type.isInterface()) {
						status.setWarning(NewWizardMessages.getFormattedString("NewTypeWizardPage.warning.SuperClassIsNotClass", sclassName)); 
						return status;
					}
					int flags= type.getFlags();
					if (Flags.isFinal(flags)) {