I agree with Stuart Marks that list == null ? Stream.empty() : list.stream() is the right way to do this (see his answer), or at least the right way to do this pre-Java 9 (see edit below), but I’ll leave this answer up to demonstrate usage of the Optional API. <T> Stream<T> getStream(List<T> list) { … Read more
Why not just do the following: Collection<string> collection = new Collection<string>(theList); as Collection(IList input) takes a List as part of construction.
Functional Java has zip, zipWith and zipIndex the way you would expect from Haskell or Scala. (Indeed, the authors are pretty much all Haskell programmers.)
You are looking for a multiset. Python’s closest datatype is collections.Counter: A Counter is a dict subclass for counting hashable objects. It is an unordered collection where elements are stored as dictionary keys and their counts are stored as dictionary values. Counts are allowed to be any integer value including zero or negative counts. The … Read more
Use Collectors.toSet : Set<String> results = someDao.findByType(type) .stream() .map(ClassName::getValue) .collect(Collectors.toSet());
The easy way to think of it is: Collections beat object arrays in basically every single way. Consider: A collection can be mutable or immutable. A nonempty array must always be mutable. A collection can allow or disallow null elements. An array must always permit null elements. A collection can be thread-safe; even concurrent. An … Read more
You should use find method on sequences. Generally you should prefer built-in methods, because they might be optimised for a specific sequence. Console println List(1,2,3,4,5).find( _ == 5) res: Some(5) That is, to return first SimpleDateFormat that match: val str = “1903 January” val formats = List(“MMM yyyy”, “yyyy MMM”, “MM yyyy”, “MM, yyyy”) .map(new … Read more
From the Javadocs The Iterator provided in method iterator() is not guaranteed to traverse the elements of the PriorityQueue in any particular order. If you need ordered traversal, consider using Arrays.sort(pq.toArray()). There are probably other equivalent mechanisms.
Use this method Collections.sort(List,Comparator) . Implement a Comparator and pass it to Collections.sort(). class RecipeCompare implements Comparator<Recipe> { @Override public int compare(Recipe o1, Recipe o2) { // write comparison logic here like below , it’s just a sample return o1.getID().compareTo(o2.getID()); } } Then use the Comparator as Collections.sort(recipes,new RecipeCompare());
You’re trying to cast the collection of values to a single ExceptionLifeCycleDataBean. You can very easily get the list though: List<ExceptionLifeCycleDataBean> beans = new ArrayList<ExceptionLifeCycleDataBean>(transitionHash.values()); Or to add to an existing collection, with: cardholderDataRecords.addAll(transitionHash.values()); No casts necessary.