hashmap

问题 I know the difference between Hashtable and HashMap. However, both these classes seemingly are using a hash function to get the job done. Is there a difference between the hash function used in Hashtable, and the hash function used in HashMap? In particular, is there a difference between the hashing algorithm they use? What is the formula used to hash in these two classes? In other words, is the way for calculating index (hash value) different? 回答1: In particular, is there a difference

问题 I know the difference between Hashtable and HashMap. However, both these classes seemingly are using a hash function to get the job done. Is there a difference between the hash function used in Hashtable, and the hash function used in HashMap? In particular, is there a difference between the hashing algorithm they use? What is the formula used to hash in these two classes? In other words, is the way for calculating index (hash value) different? 回答1: In particular, is there a difference

问题 I have a nested HashMap with String keys that contains either List , Map , or String values. I would like to flatten them like the below. Here is the data: import java.util.*; import java.util.stream.*; public class MyClass { public static void main(String args[]) { Map<String, Object> dates = new HashMap<String, Object>() {{ put("1999", new HashMap<String, Object>() {{ put("3", Arrays.asList("23", "24", "25")); put("4", Arrays.asList("1", "2", "3")); }}); put("2001", new HashMap<String,

问题 I have the following code which group the users with same age and highest score among them. I have now instead of Map<Person, List<String>> one object called Person and in the person class there Map Map<String,Double> nameScoreTogether; . I need to store the output in the map of the person object with its informations(name and the corresponding score), so how can i change the code accordingly ? Input: In data type of Map<Person, String> : {Person has at Age: 12 (Score: 50) =alex, Person has

问题 I have the following code which group the users with same age and highest score among them. I have now instead of Map<Person, List<String>> one object called Person and in the person class there Map Map<String,Double> nameScoreTogether; . I need to store the output in the map of the person object with its informations(name and the corresponding score), so how can i change the code accordingly ? Input: In data type of Map<Person, String> : {Person has at Age: 12 (Score: 50) =alex, Person has

问题 I wanna map given strings from a text file to blocks, I mean actually draw blocks. I already have a BLOCK class which works, with the following constructor: public class Block implements Collidable, Sprite, HitNotifier { private List<HitListener> hitListeners; private Color color; private Rectangle rectangle; /** * Instantiates a new collidable Block. * * @param rectangle a given rectangle * @param color the color of the block */ public Block(Rectangle rectangle, Color color) { this.color =

问题 I have a file that contains millions of rows of data. Each row has a unique id and the id series are many times not in order, and can contain holes. 1, 2, 10, 6, 3, 18 for example. I want to be able to quickly access the rows by ID, so I'm thinking storing them in a HashMap could be a viable solution, but this feels like overkill when they could be stored in a Vec . Is storing them in a Vec a good solution when the holes in the series can get pretty large ( 1, 2, 3, 1000000, 1000001... and so

问题 I am trying to convert a map value to String . I tried toString() method but it still returns an Object instead of String response = WS.sendRequest(findTestObject('api/test/TD-4_01_01-Valid')) Map parsed = response.getHeaderFields() String messageId = parsed.get('x-message-id').toString(); println messageId Actual Output: [C5yZC5hcy5sb2NhbC0xMjgyNi05MzE1LTE=] Expected Output: C5yZC5hcy5sb2NhbC0xMjgyNi05MzE1LTE= 回答1: ResponseObject#getHeaderFields returns a Map of String keys to a List of

问题 I might be confused between hashmap in Java, and map / dict in Python. I thought that the hash (k/v abstraction) of Java is kind of the same as dict in Python But then what does the map datatype do? Is it the same abstraction as the hashmap abstraction? If so, then how is it different from dictionary? I went through the docs, but it took me to whole together different paradigm: functional programming. 回答1: Map is not a datatype in python. It applies a function to a series of values and

问题 I might be confused between hashmap in Java, and map / dict in Python. I thought that the hash (k/v abstraction) of Java is kind of the same as dict in Python But then what does the map datatype do? Is it the same abstraction as the hashmap abstraction? If so, then how is it different from dictionary? I went through the docs, but it took me to whole together different paradigm: functional programming. 回答1: Map is not a datatype in python. It applies a function to a series of values and