this piece of code in removeDuplicateByValue method is not enough to remove duplicate element from hashmap? if i simply call this method in main, it throws Exception in main. why so?

Question about the task

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HashMap<String, String> copy = new HashMap<String, String>(map); for (Map.Entry<String, String> pair : copy.entrySet()) { if (pair.getValue().equals(value)) map.remove(pair.getKey()); }

Create a Map<String, String> and add ten entries that represent (last name, first name) pairs.
Remove people with the same first name.

Requirements:

The program should not display text on the screen.
The program should not read values from the keyboard.
The createMap() method must create and return a HashMap that has (String, String) elements and contains 10 entries.
The removeFirstNameDuplicates() method must remove from the map all people who have the same first name.
The removeFirstNameDuplicates() method must call the removeItemFromMapByValue() method.

package com.codegym.task.task08.task0817; import java.util.HashMap; import java.util.Map; import java.util.ArrayList; /* We don't need repeats */ public class Solution { public static HashMap<String, String> createMap() { //write your code here HashMap<String, String> map = new HashMap<String, String>(); map.put("verma","sunil"); map.put("bamotra","sourav"); map.put("kumar","vinod"); map.put("pandotra","samant"); map.put("bangotra","gourav"); map.put("lata","kanchan"); map.put("mittal","ashok"); map.put("ambani","anil"); map.put("mangeshkar","lata"); map.put("kaur","manpreet"); return map; } public static void removeFirstNameDuplicates(Map<String, String> map) { //write your code here HashMap<String, String> map2 = new HashMap<String, String>(map); ArrayList<String> list = new ArrayList<>(map2.values()); for(int i=0; i<list.size(); i++) { removeItemFromMapByValue(map2,list.get(i)); } } public static void removeItemFromMapByValue(Map<String, String> map, String value) { HashMap<String, String> copy = new HashMap<String, String>(map); for (Map.Entry<String, String> pair : copy.entrySet()) { if (pair.getValue().equals(value)) map.remove(pair.getKey()); } } public static void main(String[] args) { } }

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Misiu

Level 41 , Gdansk, Poland

11 August 2020, 10:58

Your code doesn't solve the task. Show the code that throws exception.

sourav bamotra

Level 20 , jammu, India

11 August 2020, 11:17

nope, fourth condition not passed. i was trying the same set of code on my IDE, but i excluded the method part and run everything in main and the exception was coming because i wasnt using the copy of the map. i directly iterate the map whose element was suppose to be removed. so exception part is clear. but help me out with this task.

Misiu

Level 41 , Gdansk, Poland

11 August 2020, 11:35

useful

I have two nested iterations and one IF on the map. for ([pair1]) for ([pair2]) if ([the same values] but not [the same keys]) removeItemFromMapByValue(map, [doubled value])

sourav bamotra

Level 20 , jammu, India

12 August 2020, 16:36

ok misiu, i actually figured it out. took me some time. but finally passed the task. thank you :)

Misiu

Level 41 , Gdansk, Poland

11 August 2020, 09:51

The code is correct. But what value(s) do you pass to it? Passed value has to be one of duplicated values.

sourav bamotra

Level 20 , jammu, India

11 August 2020, 10:29

misiu kindly check again, i attached my code as well. i just wanted to know if i simply call the method that removes the duplicate element from the map, in other method and call that method in main. then why it is throwing exception.