👀 Views: 73 💬 Answers: 1 📅 Created: 2025-05-31

java concurrent-modification streams Java

I'm upgrading from an older version and I'm converting an old project and I'm not sure how to approach I've been banging my head against this for hours..... I've looked through the documentation and I'm still confused about I'm working with a `ConcurrentModificationException` when trying to process a `List<String>` using Java Streams in my application... I've ensured that I'm not modifying the list directly, but I still face this scenario intermittently. Here's the relevant code snippet: ```java import java.util.ArrayList; import java.util.List; import java.util.stream.Collectors; public class StreamExample { public static void main(String[] args) { List<String> items = new ArrayList<>(); items.add("apple"); items.add("banana"); items.add("cherry"); // Simulating a modification in another thread new Thread(() -> { try { Thread.sleep(50); items.add("date"); // This should not interfere with the stream processing } catch (InterruptedException e) { e.printStackTrace(); } }).start(); List<String> filteredItems = items.stream() .filter(item -> item.startsWith("b")) .collect(Collectors.toList()); System.out.println(filteredItems); } } ``` I'm using Java 11, and I expected that the stream operations would be safe if the modifications happen in a separate thread. However, I keep getting the following behavior message: ``` Exception in thread "main" java.util.ConcurrentModificationException at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1043) at java.base/java.util.ArrayList$Itr.next(ArrayList.java:997) at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) ... ``` I've tried synchronizing the list access using `Collections.synchronizedList(new ArrayList<>())`, but it doesn't seem to help either. What am I missing here? Is there a better way to handle concurrent modifications while processing streams in Java? I want to ensure thread safety without sacrificing performance. Any insights or suggestions would be appreciated! For context: I'm using Java on macOS. Any help would be greatly appreciated! My development environment is Linux. This is part of a larger mobile app I'm building. Could someone point me to the right documentation? Is there a simpler solution I'm overlooking? What am I doing wrong?