Ошибка ConcurrentModificationException

removeItemFromMapByValue(map, currentName);

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1479)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1477)
	at com.javarush.task.task08.task0817.Solution.removeTheFirstNameDuplicates(Solution.java:43)
	at com.javarush.task.task08.task0817.Solution.main(Solution.java:67)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)

package com.javarush.task.task08.task0817;

import java.util.HashMap;
import java.util.Map;
import java.util.Iterator;
import java.util.Set;
import java.util.HashSet;

/*
Нам повторы не нужны
*/

public class Solution {
    public static Map<String, String> createMap() {
        //напишите тут ваш код
        Map<String, String> persons = new HashMap<>();

        persons.put("A1", "B");
        persons.put("A2", "C");
        persons.put("A3", "D");
        persons.put("A4", "B");
        persons.put("A5", "E");

        persons.put("A6", "B");
        persons.put("A7", "B");
        persons.put("A8", "F");
        persons.put("A9", "B");
        persons.put("A10", "G");

        return persons;

    }

    public static void removeTheFirstNameDuplicates(Map<String, String> map) {
        //напишите тут ваш код
        Set<String> passedNames = new HashSet<>();

        String currentName;

        Iterator<Map.Entry<String, String>> iter = map.entrySet().iterator();
        while(iter.hasNext()) {
            Map.Entry<String, String> pair = iter.next();
            currentName = pair.getValue();

            if (passedNames.contains(currentName)) {
                removeItemFromMapByValue(map, currentName);
            }

            passedNames.add(currentName);
        }

    }

    public static void removeItemFromMapByValue(Map<String, String> map, String value) {
        Map<String, String> copy = new HashMap<>(map);
        for (Map.Entry<String, String> pair : copy.entrySet()) {
            if (pair.getValue().equals(value)) {
                map.remove(pair.getKey());
            }
        }
        System.out.println(copy);
    }

    public static void main(String[] args) {
        Map<String, String> map = createMap();
        removeTheFirstNameDuplicates(map);

public static void removeTheFirstNameDuplicates(Map<String, String> map) {
    //напишите тут ваш код
    Map<String, String> copy = new HashMap<>(map);
    Set<String> passedNames = new HashSet<>();

    String currentName;

    Iterator<Map.Entry<String, String>> iter = copy.entrySet().iterator();
    while(iter.hasNext()) {
        Map.Entry<String, String> pair = iter.next();
        currentName = pair.getValue();

        if (passedNames.contains(currentName)) {
            removeItemFromMapByValue(map, currentName);
        }
        passedNames.add(currentName);
    }
}