collections

问题 String currency = EUR; List<Payment> payments = #has payments, with one field being Currency; //This is not it: payments.sort(Comparator.comparing(o -> o.getCurrency().equals(currency)); I want all the payments which currency equals to variable currency in my case EUR to be at the top of the list, others order stays the same. And if there is nothing that equals with the variable currency then sort by default value which for example is USD. I know this can be done other ways, but this is kind

问题 String currency = EUR; List<Payment> payments = #has payments, with one field being Currency; //This is not it: payments.sort(Comparator.comparing(o -> o.getCurrency().equals(currency)); I want all the payments which currency equals to variable currency in my case EUR to be at the top of the list, others order stays the same. And if there is nothing that equals with the variable currency then sort by default value which for example is USD. I know this can be done other ways, but this is kind

问题 I have two lists list1 & list2 of type List Term{ long sId; int rowNum; long psid; String name; } List<Term> list1 = new ArrayList<>(); List<Term> list2 = new ArrayList<>(); I want to return all the items from list1 where (list1.psid != list2.psid). I tried this but its not working public List<Term> getFilteredRowNum(List<Term> list1, List<Term> list2) { List<Long> psid = list2.stream().map(x -> x.getPsid()).collect(Collectors.toList()); return list1.stream().filter(x -> !psid.contains(x

问题 How to split an iterator into a prefix with duplicates and the rest ? For instance, def splitDupes(it: Iterator[Int]): (Iterator[Int], Iterator[Int]) = ??? val (xs, ys) = splitDupes(List(1, 1, 1, 2, 3, 4, 5).iterator) xs.toList // List(1, 1, 1) ys.toList // List(2, 3, 4, 5) val (xs, ys) = splitDupes(List(1, 2, 3, 4, 5).iterator) xs.toList // List(1) ys.toList // List(2, 3, 4, 5) val (xs, ys) = splitDupes(List(1, 1, 1, 1, 1).iterator) xs.toList // List(1, 1, 1, 1, 1) ys.toList // List() val

问题 How to split an iterator into a prefix with duplicates and the rest ? For instance, def splitDupes(it: Iterator[Int]): (Iterator[Int], Iterator[Int]) = ??? val (xs, ys) = splitDupes(List(1, 1, 1, 2, 3, 4, 5).iterator) xs.toList // List(1, 1, 1) ys.toList // List(2, 3, 4, 5) val (xs, ys) = splitDupes(List(1, 2, 3, 4, 5).iterator) xs.toList // List(1) ys.toList // List(2, 3, 4, 5) val (xs, ys) = splitDupes(List(1, 1, 1, 1, 1).iterator) xs.toList // List(1, 1, 1, 1, 1) ys.toList // List() val

问题 This is a follow up of this excellent question C# Sort and OrderBy comparison. I will use the same example: List<Person> persons = new List<Person>(); persons.Add(new Person("P005", "Janson")); persons.Add(new Person("P002", "Aravind")); persons.Add(new Person("P007", "Kazhal")); The methods in contention are: persons.Sort((p1, p2) => string.Compare(p1.Name, p2.Name, true)); //and persons.OrderBy(n => n.Name); Let me start by saying that I understand there isn't any significant performance

问题 This is a follow up of this excellent question C# Sort and OrderBy comparison. I will use the same example: List<Person> persons = new List<Person>(); persons.Add(new Person("P005", "Janson")); persons.Add(new Person("P002", "Aravind")); persons.Add(new Person("P007", "Kazhal")); The methods in contention are: persons.Sort((p1, p2) => string.Compare(p1.Name, p2.Name, true)); //and persons.OrderBy(n => n.Name); Let me start by saying that I understand there isn't any significant performance

问题 Whats the best way of doing it? var set2 = new HashSet<reference_type>(); Traverse the set with a foreach like this. foreach (var n in set) set2.Add(n); Or use something like union like this. set2 = set.UnionWith(set); // all the elements 回答1: Use the constructor: HashSet<type> set2 = new HashSet<type>(set1); Personally I wish LINQ to Objects had a ToHashSet extension method as it does for List and Dictionary . It's easy to create your own of course: public static HashSet<T> ToHashSet<T>(this

问题 Whats the best way of doing it? var set2 = new HashSet<reference_type>(); Traverse the set with a foreach like this. foreach (var n in set) set2.Add(n); Or use something like union like this. set2 = set.UnionWith(set); // all the elements 回答1: Use the constructor: HashSet<type> set2 = new HashSet<type>(set1); Personally I wish LINQ to Objects had a ToHashSet extension method as it does for List and Dictionary . It's easy to create your own of course: public static HashSet<T> ToHashSet<T>(this

问题 The assertAlmostEqual(x, y) method in Python's unit testing framework tests whether x and y are approximately equal assuming they are floats. The problem with assertAlmostEqual() is that it only works on floats. I'm looking for a method like assertAlmostEqual() which works on lists of floats, sets of floats, dictionaries of floats, tuples of floats, lists of tuples of floats, sets of lists of floats, etc. For instance, let x = 0.1234567890 , y = 0.1234567891 . x and y are almost equal because