👀 Views: 88 💬 Answers: 1 📅 Created: 2025-06-16

java arrays concurrent-modification Java

I've encountered a strange issue with I just started working with I've searched everywhere and can't find a clear answer... I'm currently facing a `ConcurrentModificationException` when trying to filter elements from an `ArrayList` in Java. I'm using Java 11 and have a list of `String` objects that I want to filter based on a certain criterion. My initial approach was to use a standard `for` loop with an `Iterator`, but I'm still running into issues. Here's the relevant part of my code: ```java import java.util.ArrayList; import java.util.Iterator; public class ArrayListFilter { public static void main(String[] args) { ArrayList<String> fruits = new ArrayList<>(); fruits.add("apple"); fruits.add("banana"); fruits.add("cherry"); fruits.add("date"); // Attempt to filter out fruits that start with 'a' for (String fruit : fruits) { if (fruit.startsWith("a")) { fruits.remove(fruit); // This line causes ConcurrentModificationException } } } } ``` I know that modifying a collection while iterating through it with a `for-each` loop is not allowed, but I thought removing items via an iterator would be fine. I tried changing my filtering logic to use an `Iterator` explicitly: ```java Iterator<String> iterator = fruits.iterator(); while (iterator.hasNext()) { String fruit = iterator.next(); if (fruit.startsWith("a")) { iterator.remove(); // This should work without exceptions } } ``` Yet, I'm still getting the exception. I've also looked into using Java streams with filters, but I'm unsure how to do this effectively while maintaining the original list. Any advice on how to properly filter my `ArrayList` without running into these concurrent modification issues would be greatly appreciated! This is part of a larger web app I'm building. Any ideas what could be causing this? My team is using Java for this service. This is happening in both development and production on Windows 11. What's the best practice here? Hoping someone can shed some light on this.