Unexpected ConcurrentModificationException When Iterating Over a HashMap in Java 8
Does anyone know how to I'm a bit lost with I'm optimizing some code but I've spent hours debugging this and I'm working on a personal project and I'm encountering a `ConcurrentModificationException` when I try to iterate over a `HashMap` in Java 8 while simultaneously modifying it. Here’s the code I’m working with: ```java import java.util.HashMap; import java.util.Iterator; import java.util.Map; public class HashMapExample { public static void main(String[] args) { Map<String, Integer> myMap = new HashMap<>(); myMap.put("A", 1); myMap.put("B", 2); myMap.put("C", 3); Iterator<Map.Entry<String, Integer>> iterator = myMap.entrySet().iterator(); while (iterator.hasNext()) { Map.Entry<String, Integer> entry = iterator.next(); System.out.println(entry.getKey() + " : " + entry.getValue()); // Trying to modify the map while iterating if (entry.getKey().equals("B")) { myMap.put("D", 4); // Adding a new entry // Attempting to remove the current entry iterator.remove(); } } } } ``` When I run this code, I get the following error: ``` Exception in thread "main" java.util.ConcurrentModificationException at java.base/java.util.HashMap$HashIterator.nextNode(HashMap.java:1557) at java.base/java.util.HashMap$KeyIterator.next(HashMap.java:1588) at HashMapExample.main(HashMapExample.java:12) ``` I tried using `iterator.remove()` to remove the current entry, but it still throws the exception. I thought that modifying the map only through the iterator would be safe, but it appears this isn’t the case. What am I missing? Is there a better approach to safely modify the `HashMap` while iterating over its entries? Any suggestions for how to fix this would be appreciated! Is there a better approach? My team is using Java for this CLI tool. Am I approaching this the right way? Could someone point me to the right documentation? I've been using Java for about a year now.