hashmap

问题 This is related to Working with dictionaries/lists in R, where we try to create a key-value style dictionary with vectors, but now about how to access the values. I can get the keys in the following way foo <- c(12, 22, 33) names(foo) <- c("tic", "tac", "toe") names(foo) [1] "tic" "tac" "toe" and I can access the elements > lapply(FUN=function(a){foo[[a]]},X = 1:length(foo)) [[1]] [1] 12 [[2]] [1] 22 [[3]] [1] 33 and then I can do unlist(lapply(FUN=function(a){foo[[a]]},X = 1:length(foo))) [1

问题 I have a class representing a set of values that will be used as a key in maps. This class is immutable and I want to make it a singleton for every distinct set of values, using the static factory pattern. The goal is to prevent identical objects from being created many (100+) times and to optimize the equals method. I am looking for the best way to cache and reuse previous instances of this class. The first thing that pops to mind is a simple hashmap, but are there alternatives? 回答1: There

问题 Say I have the following class: class A { String name; Double value; } and a list of the above class objects which might have: [{f 2.1}, {c 1.1}, {a 0.3}... and so on] [{n 0.5}, {f 1.9}, {x 0.1}, {a 1.9}, {b 1.1}... and so on] ... and so on all I want is to do the followings: 1. Building power subsets from the internal list items(N.B: skip the single subsets). 2. Push the subset in another List as an object of the above class A like this: a. if f,c is a subset of 1st element then f,c would be

问题 Say I have the following class: class A { String name; Double value; } and a list of the above class objects which might have: [{f 2.1}, {c 1.1}, {a 0.3}... and so on] [{n 0.5}, {f 1.9}, {x 0.1}, {a 1.9}, {b 1.1}... and so on] ... and so on all I want is to do the followings: 1. Building power subsets from the internal list items(N.B: skip the single subsets). 2. Push the subset in another List as an object of the above class A like this: a. if f,c is a subset of 1st element then f,c would be

问题 I have followed this post Binding hashmap with tableview (JavaFX) and created a TableView that is populated by data from a HashMap. The TableView receives its data from a HashMap called map by creating an ObservableList from map.entrySet() and handing that ObservableList off to the TableView 's constructor. (Code is below) However, although it's an ObservableList with SimpleStringProperty s, the TableView does not update when changes are made to the underlying HashMap. Here is my code: public

问题 I tried to write a small program to demonstrate hash collisions in java when only equals is overridden and not hashcode() method. This was to prove the theory that two unequal objects can have the same hashcode. This was for an Interview question where the behaviour was asked. I created 200,000 objects, stored them in an array and then compared them to see which are duplicates. (For this I am using a nested for loop iterating over an array of objects after the object creation phase.) For

问题 This is an extension for Android implement Parcelable object which has hashmap but mine is a little different. I have these classes public class EventDetails implements Parcelable { Private String id; Private String eventName; Private Long eventUnixTime; Private HashMap <String, User> pickedUser = null; } and public class User implements Parcelable { private String email; private String userName; private String userPicture; private Boolean hasLoggedInWithPassword; private HashMap<String,

问题 This is an extension for Android implement Parcelable object which has hashmap but mine is a little different. I have these classes public class EventDetails implements Parcelable { Private String id; Private String eventName; Private Long eventUnixTime; Private HashMap <String, User> pickedUser = null; } and public class User implements Parcelable { private String email; private String userName; private String userPicture; private Boolean hasLoggedInWithPassword; private HashMap<String,

问题 I have a hash map that looks like this: HashMap<String, ArrayList<String>> varX = new HashMap<String, ArrayList<String>>(); And I can't for the life of me work out how to count the number of duplicate values. For example, If put("001", "DM"); into the hash map and put("010", "DM"); as well, how can count if there are two values int the ArrayList section of the Hashmap. For example, the output would look something like this: DM:2 as I 'put' two DM values into the Hashmap. 回答1: You have a

问题 Is there a way to create a hash of hashes in C++? Effectively I am trying to do what you can do in Perl but only in C++. Here is an example of Perl code I would like to have happen in C++ %hash = ( gameobject1 => { position => { x_loc => 43, y_loc => 59, } rect_size => { width => 5, height => 3, } collidable => 1, sounds => { attack => "player_attack.ogg", jump => "player_jump1.ogg", jump_random => [qw/player_jump1.ogg player_jump2.ogg player_jump3.ogg/] } }, gameobject2 => { position => { x