The key to understanding this problem is to realize that there are two different ways to build and work with collections in the collections library. One is the public collections interface with all its nice methods. The other, which is used extensively in creating the collections library, but which are almost never used outside of … Read more
A more idiomatic approach would be to use MutableList instead of specifically ArrayList. You can declare: val listOfVehicleNames: MutableList<String> = mutableListOf() And add to it that way. Alternatively, you may wish to prefer immutability, and declare it as: var listOfVehicleNames: List<String> = emptyList() And in your completion block, simply reassign it: listOfVehicleNames = response.body()?.message()?.orEmpty() .map … Read more
Try the commons collections API: List<Cat> bigList = ….; // master list Collection<Cat> smallList = CollectionUtils.select(bigList, new Predicate() { public boolean evaluate(Object o) { Cat c = (Cat)o; return c.getFavoriteFood().equals(“Wiskas”) && c.getWhateverElse().equals(Something); } }); Of course you don’t have to use an anonymous class every time, you could create implementations of the Predicate interface for … Read more
I think the first line means that when I call x[k] for a nonexistent key k (such as a statement like v=x[k]), the key-value pair (k,0) will be automatically added to the dictionary, as if the statement x[k]=0 is first executed. That’s right. This is more idiomatically written x = defaultdict(int) In the case of … Read more
Yes; just uses braces instead of parentheses. var nvc = new NameValueCollection { {“a”, “1”}, {“b”, “2”} }; You can call Add methods with arbitrary sets of parameters using the syntax.
A new array is created and the contents of the old one are copied over. That’s all you know at the API level. Quoting from the docs (my emphasis): Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at … Read more
var names = new Dictionary<int, string> { { 1, “Adam” }, { 2, “Bart” }, { 3, “Charlie” } };
Java 8 way of doing it:- List<Integer> idList = students.stream().map(Student::getId).collect(Collectors.toList());
You can use $lookup ( multiple ) to get the records from multiple collections: Example: If you have more collections ( I have 3 collections for demo here, you can have more than 3 ). and I want to get the data from 3 collections in single object: The collection are as: db.doc1.find().pretty(); { “_id” … Read more
ConcurrentSkipListSet and ConcurrentSkipListMap are useful when you need a sorted container that will be accessed by multiple threads. These are essentially the equivalents of TreeMap and TreeSet for concurrent code. The implementation for JDK 6 is based on High Performance Dynamic Lock-Free Hash Tables and List-Based Sets by Maged Michael at IBM, which shows that … Read more