void (GrCodeReferenceElement[] refs, Collection<? super String> classes, Collection<? super String> interfaces, Collection<? super String> unknown) { for (GrCodeReferenceElement ref : refs) { final PsiElement extendsElement = ref.resolve(); String canonicalText = ref.getCanonicalText(); if (extendsElement instanceof PsiClass) { if (((PsiClass)extendsElement).isInterface()) { interfaces.add(canonicalText); } else { classes.add(canonicalText); } } else { unknown.add(canonicalText); } } }