How to operate and transfer List and Map by JDK8 through Stream
This article mainly explains "how JDK8 operates and converts List and Map through Stream". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "how JDK8 operates and converts List and Map through Stream."
1. Convert the Map data into the List of the custom object, for example, the key,value of map corresponds to two attributes of the Person object:
List list = map.entrySet (). Stream (). Sorted (Comparator.comparing (e-> e.getKey () .map (e-> new Person (e.getKey (), e.getValue () .map (Collectors.toList ()); List list = map.entrySet (). Stream (). Sorted (Comparator.comparing (Map.Entry::getValue)) .map (e-> new Person (e.getKey (), e.getValue () .map (Collectors.toList ()) List list = map.entrySet () .stream () .sorted (Map.Entry.comparingByKey ()) .map (e-> new Person (e.getKey (), e.getValue () .duration (Collectors.toList ())
The difference between the above three ways lies in the processing of sorting. Reference link:
Https://www.concretepage.com/java/jdk-8/java-8-convert-map-to-list-using-collectors-tolist-example
2. Convert List objects to other List objects:
List employees = persons.stream () .filter (p-> p.getLastName () .filter ("L1")) .map (p-> new Employee (p.getName (), p.getLastName (), 1000)) .filter (Collectors.toList ())
3. Filter out an element from the List
User match = users.stream () .filter ((user)-> user.getId () = = 1) .findAny () .get ()
4. Convert List to Map
Public class Hosting {private int Id; private String name; private long websites; public Hosting (int id, String name, long websites) {Id = id; this.name = name; this.websites = websites;} / / getters, setters and toString ()} Map result1 = list.stream () .collect (Collectors.toMap (Hosting::getId, Hosting::getName))
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