@NotNull
  public static Collection<JavaClass> getClassesInPackage(@NotNull JavaPackage javaPackage) {
    Collection<JavaClass> classes = javaPackage.getClasses();
    Set<FqName> addedQualifiedNames = new HashSet<FqName>(classes.size());
    List<JavaClass> result = new ArrayList<JavaClass>(classes.size());

    for (JavaClass javaClass : classes) {
      FqName fqName = javaClass.getFqName();
      if (fqName != null && addedQualifiedNames.add(fqName)) {
        result.add(javaClass);
      }
    }

    return result;
  }