hashmap

问题 I'm working with HashMap since few days, and facing below weird situation. Case 1:Changed Key which is already existing in HashMap, and print HashMap Case 2: Changed key which is already existing in HashMap and Put that key again into the HashMap. Print HashMap. Please find below code as well as two different output of two case. Could you please anyone let me know, whats going on in below code. import java.util.HashMap; import java.util.Set; class Emp{ private String id ; public String getId(

问题 I want to convert below json array to java hashmap using jackson and iterate the values like below: Need output like this: key Value 1 sql 2 android 3 mvc JSON Sample: enter code here { "menu": [ { "1": "sql", "2": "android", "3": "mvc" } ] } It would be really appreciated if someone can share the code to achieve this. Thanks for your help! 回答1: Here is a solution that reveals the idea: public class JacksonSerializer { public static final String INPUT = "{\n" + " \"menu\": [\n" + " {\n" + " \

问题 Hello I have a custom Hash that needs to be returned in an API. But currently I'm struggling to find a good way to do so. The following example will describe the problem. Lets say we have the following code: data = {name: "Jon", value: "13"} results = [] [1, 2, 3, 4, 5].each do |i| data[:id] = i results << data end # output # results = [{name: "Jon", value: "13", id: 5}, {name: "Jon", value: "13", id: 5}, {name: "Jon", value: "13", id: 5}, {name: "Jon", value: "13", id: 5}, {name: "Jon",

问题 I want to store my data in HashMap<Point[], Double> . I used iteration to assign the data, but when I checked at the end, the number of elements is only 1. I have implemented hashCode() and equals() in the custom class Point. HashMap<Point[], Double> hmDistOrd = new HashMap<Point[], Double>(); Point[] keyPts = new Point[2]; for (int i=0; i<intersectionPts.size(); i++) { p1 = intersectionPts.get(i); for (int j=0; j<intersectionPts.size(); j++) { p2 = intersectionPts.get(j); if (!p1.equals(p2))

问题 I explain what I am trying to do in comments above the parts in the method: public int addPatron(String name) throws PatronException { int i = 0; //1. Iterate through a hashmap, and confirm the new name I am trying to add to the record doesn't already exist in the hashmap for (Map.Entry<Integer, Patron> entry : patrons.entrySet()) { Patron nameTest = entry.getValue(); //2. If the name I am trying to add already exists, we want to throw an exception saying as much. if (nameTest.getName() ==

问题 I created a class Person (as the book says) to hold the name and last name of a person entered from the keyboard and then there is another class PhoneNumber which encapsulates the country code, area code and the number of a person as a String. Person is intended to be used as the key in a Hashmap. Class BookEntry encapsulates both Person and PhoneNumber . A lot of BookEntry objects make up a HashMap that represents a phonebook. Person implements Comparable<Person> so it contains CompareTo

问题 I have been doing some performance checks with HashMap on Java. The results are surprising i should say. I would show the code first. public class HashMapCheck { int m_size =10; String Keys[], Values[] ; void initKeyValues(int size){ m_size=size; Keys = new String[m_size]; Values = new String[m_size]; for(int i=0;i<m_size;i++) { Keys[i]="key"+i; Values[i] ="value"+ i; } } public void withOutInitialCapacity(){ long start= System.nanoTime(); HashMap hm = new HashMap(); long hmEnd=System

问题 I am facing a problem creating a Json which is actually a complex one and i need to create it through HashMap only..I was actually looking for some recursive function that could be a best solution to my problem. JSON i need to create looks like.. {"pkt":{ "data2":{"z":"3", "y":"2", "x":"1"}, "data3":{"n":"3", "l":"1", "m":"2"}, "mid":"1328779096525", "data1":{"b":"2", "c":"3", "a":"1"}, "msg":"10012" } } any ideas?? 回答1: We're using GSON for our object/JSON conversions. Here's a link for more

问题 This question already has answers here : Iterate through a HashMap [duplicate] (7 answers) Closed last year . In the following piece of code, I am saving firstname and emailId of a person in a hashmap.I wish to print the firstname of the entries that have emailId ending with 'gmail.com' in ascending order. for that I have used TreeMap class of java. but the problem is printing the keys where emailId pattern matches.. public class RegExSolution { public static void main(String[] args) {

问题 I am coding in blueJ and what I am trying to do is this: 1.a) Create a getWordSet() method in WordGroup which: takes another WordGroup object as a parameter creates a HashSet<String> uses two for loops to put all the words from this and the parameter WordGroup into the HashSet returns the HashSet<String> 1.b) In the main method: use the getWordSet() method using the two WordGroup s iterate or loop over the HashSet returned and print the words from it 2.a) Create a method in the WordGroup