Failing to pass task 3 and 4

Question about the task

Under discussion

I'm calling the removeItemFromMapByValue method in my removeFirstNameDuplicates method but it's not working. I'm completely stumped on this. Your help is appreciated.

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.Iterator; import java.util.Set; import java.util.*; /* 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("a","one"); map.put("b","two"); map.put("c","three"); map.put("d","four"); map.put("e","five"); map.put("f","six"); map.put("g","seven"); map.put("h","eight"); map.put("i","nine"); map.put("j","ten"); return map; } public static void removeFirstNameDuplicates(Map<String, String> map) { //write your code here HashMap<String, String> duplicatMap = new HashMap<>(); Iterator<Map.Entry<String,String>> iter = map.entrySet().iterator(); while (iter.hasNext()) { Map.Entry<String,String> entry = iter.next(); String value = entry.getValue(); if(duplicatMap.containsKey(value)) { //duplicatMap.remove(value); removeItemFromMapByValue(map, value); } } } 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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Guadalupe Gagnon

Level 37 , Tampa, United States

15 July 2020, 15:33

You can not iterate over a collection, such as a Map, while removing objects from that collection other than by using the Iterator's method remove(). Doing so will create a concurrent modification exception and crash the code. You are going to need to figure out how to remove items from the collection while not looping through that same collection.

dnlklnhfr

Level 30 , Karlsruhe, Germany

15 July 2020, 15:54

agreed and on top it actually starts even earlier in the code: line 32: the duplicated map remains empty if it doesn't get the map passed to initialize. line 39: I guess it should be .containsValue rather than .containsKey otherwise this if-statement will never ever be entered

Maxine Hammett

Level 19 , San Diego, United States

15 July 2020, 16:56

I copied the map into my duplicate map and changed the .containKey to .containsValue. But it's still not passing the removeFirstNameDuplicates() method.

public static void removeFirstNameDuplicates(Map<String, String> map) {
    // Creating a new hash map and copying
    HashMap<String, String> duplicatMap = new HashMap<String, String>();
    duplicatMap.putAll(map);
    Iterator<Map.Entry<String,String>> iter = map.entrySet().iterator();
    while (iter.hasNext()) {
        Map.Entry<String,String> entry = iter.next();
        String value = entry.getValue();

        if(duplicatMap.containsValue(value)) {
           removeItemFromMapByValue(map, value);
        }
    }
}

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());
    }
}

Maxine Hammett

Level 19 , San Diego, United States

15 July 2020, 17:18

Got it working!

public static void removeFirstNameDuplicates(Map<String, String> map) {
    // Creating a new hash map and copying
 ArrayList<String> test = new ArrayList<>();

    for(Map.Entry<String, String> pair : map.entrySet()){
        if(!test.contains(pair.getValue())) test.add(pair.getValue());
        else{
            removeItemFromMapByValue(map, pair.getValue());
            removeFirstNameDuplicates(map);
            break;
        }
    }
}