Please help - I cant work out a resolve to meet the final 2 requirements

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I have been at this for a day, it works, matches the initial criteria, however the error I keep getting is that I've mixed up the input order. I rectified this by using a LinkedHashmap and cloning it back to the originally declared HashMap variable. I know it needs to read the pairs into this HashMap table directly, however it changes the order from order of user input, to order by String Hash key value. I know why it's failing, I just don't know how to resolve it. Any pointers would be appreciated

Task: The program reads a pair (a number and string) from the keyboard and displays it on the screen.
New task: The program reads pairs (a number and string) from the keyboard and stores them in a HashMap.
Any empty input signifies the end of data entry.
The numbers can be repeated.
The strings are always unique.
The entered data must not be lost!
The program then displays the contents of the HashMap on the screen.
Each pair on a new line.

Example input:
1 Sam 2 I 1 Am

Example output:
1 Sam 2 I 1 Am

Requirements:

The program must read data from the keyboard.
The program should display text on the screen.
In the main method, declare a HashMap variable and immediately initialize it.
The program should put the pairs read from the keyboard into the HashMap.
The program should display the contents of the HashMap in accordance with the conditions. The key and value are separated by a space. Each value should be on a new line.

package com.codegym.task.task10.task1019; import java.io.*; import java.util.*; /* Functionality is not enough! */ public class Solution { public static void main(String[] args) throws IOException { HashMap<String, Integer> map2 = new HashMap<>(); LinkedHashMap<String, Integer> map1 = new LinkedHashMap<>(); BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); try { while (true) { //name is blank int id = Integer.parseInt(reader.readLine()); String name = reader.readLine(); map1.put(name, id); if (name.isEmpty()) { map1.remove(name, id); break; } } } catch (NumberFormatException r) { while (true) { //id is blank try { Integer id = Integer.parseInt(reader.readLine()); String name = reader.readLine(); map1.put(name, id); } catch (NumberFormatException s) { break; } } } map2 = (HashMap<String, Integer>) map1.clone(); for (Map.Entry<String, Integer> map : map2.entrySet()) { String index = map.getKey(); Integer value = map.getValue(); System.out.println( index + " " + value); } } }

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Odhran

Level 18 , Sheffield, United Kingdom

9 August 2020, 22:12

solution

For anyone stuck on this, I lost an upsetting amount of time delving into the inner workings of a HashMap, my solution actually worked all the way until the last line, where the output should be value then index - this is why the order was mixed up, order of input isn't important here, the order of output is. Found out some awesome information though: Internal HashMap Obect code explained - this whole site is worth a browse https://www.geeksforgeeks.org/internal-working-of-hashmap-java/ - also this for overriding and creating your own hash code references

Odhran

Level 18 , Sheffield, United Kingdom

8 August 2020, 12:11

Yeah I tried that but it then fails from the third condition down. Im going to try parsing the string to hex for the initial input, then sort and convert it back before the output. Just seems a bit OTT and may still fail the conditions but it'll be an interesting approach to try

Samuel Schmid

Level 4 , Rothrist, Switzerland

8 August 2020, 10:42

Have you tried using only a LinkedHashMap? Because technically a LinkedHashMap is also a HashMap, since it extends that. I dont see any way to do with without a big pain if you really need to insert it into a regular HashMap first. You will lose the insertion order that way.