collections

问题 My objective is to create a map. It have reqid , name and lowest status number of a set as a key. Here set refers to rows belonging to a specific Reqid . The value of the map is an Arraylist which consists of all rows as objects of a specific id . public class MapKey { private Integer id; private String name; private Integer status; public MapKey(Integer id, String name,Integer status) { this.id = id; this.name = name; this.status=status; } @Override toString,hashCode,equals public class

问题 I have the following question: If asked whether to use a shift vs a multiply or divide for example the answer would be, let the JVM optimize. Example here: is-shifting-bits-faster-than-multiplying Now I was looking at the jdk source, for example Priority Queue and the code uses only shifting for both multiplication and division (signed and unsigned). Taking for granted that the post in SO is the valid answer I was wondering why in jdk they prefer to do it by shifting? Is it some subtle detail

问题 There is a list of Person objects. List<Person> persons = generatePersons(); An unmodifiableList is created with it. List<Person> unmodifiableList = Collections.unmodifiableList(persons); I understand that unmodifiableList doesn't support add/remove/set operations. At the same time it is not immutable since it has a reference to an existing modifiable list persons and whenever changes are made to the persons list, the changes are reflected in unmodifiableList too. An immutable list is created

问题 I have a ViewBag that is a list which i create in the controller: List<string> listoflists = new List<string>(); it then gets filled with some string like for example: listoflists.Add("java"); listoflists.Add("php"); listoflists.Add("C#"); Adding it to the ViewBag: ViewBag.listoflists = listoflists; i then would like to check in my View if this contains a specific string: @if(ViewBag.listoflists.contains("java") { // do html stuff } but when running this i get the following error: System

问题 I have a ViewBag that is a list which i create in the controller: List<string> listoflists = new List<string>(); it then gets filled with some string like for example: listoflists.Add("java"); listoflists.Add("php"); listoflists.Add("C#"); Adding it to the ViewBag: ViewBag.listoflists = listoflists; i then would like to check in my View if this contains a specific string: @if(ViewBag.listoflists.contains("java") { // do html stuff } but when running this i get the following error: System

问题 I seem to run into this problem all the time. I want to modify some of the elements in a list, but I need to keep some state as I do it, so map doesn't work. Here is an example : scala> val l1 = List("a","b","c","d","e","f","b","c","e","b","a") l1: List[String] = List(a, b, c, d, e, f, b, c, e, b, a) I want to change the name of any duplicates. so I want to end up with this: List(a1, b1, c1, d, e1, f, b2, c2, e2, b3, a2) Getting the dupes is easy : scala> val d = l1.diff(l1.distinct).distinct

问题 I seem to run into this problem all the time. I want to modify some of the elements in a list, but I need to keep some state as I do it, so map doesn't work. Here is an example : scala> val l1 = List("a","b","c","d","e","f","b","c","e","b","a") l1: List[String] = List(a, b, c, d, e, f, b, c, e, b, a) I want to change the name of any duplicates. so I want to end up with this: List(a1, b1, c1, d, e1, f, b2, c2, e2, b3, a2) Getting the dupes is easy : scala> val d = l1.diff(l1.distinct).distinct

问题 I have a class that is receiving API data and I would like to wrap all of the responses into a collection class. So, I receive the data from the API call, turn it into a plain associative php array, and wrap it using the collect() helper. I was half expecting it to work just like Eloquent does where you can reference a key as a collection property, but it doesn't. Here is an example of response data I would receive: $data = [ 'status' => 'SUCCESS', 'message' => 'Your request was received.',

问题 I have a class that is receiving API data and I would like to wrap all of the responses into a collection class. So, I receive the data from the API call, turn it into a plain associative php array, and wrap it using the collect() helper. I was half expecting it to work just like Eloquent does where you can reference a key as a collection property, but it doesn't. Here is an example of response data I would receive: $data = [ 'status' => 'SUCCESS', 'message' => 'Your request was received.',

问题 public class Dashboard { int REQUEST_ID, PRICE, Status; String LOGIN_USER; public int getREQUEST_ID() { return REQUEST_ID; } public void setREQUEST_ID(int rEQUEST_ID) { REQUEST_ID = rEQUEST_ID; } //all getters and setters public class MapKey { private Integer id; private String name; public MapKey(Integer id, String name) { this.id = id; this.name = name; } @Override Hashcode and equals public class DBConnection { public ArrayList<Dashboard> getStoreResult() { ArrayList<Dashboard> dashRec;