Java 17: Trouble with Thread-Safety in a Custom Cache Implementation
I just started working with I'm currently working on a custom caching mechanism in Java 17 that employs a concurrent map for storage... However, I'm encountering issues with thread-safety when multiple threads attempt to read and write simultaneously. Specifically, I'm seeing inconsistent states in cached objects, which leads to unexpected behaviors. Here's a simplified version of my cache implementation: ```java import java.util.concurrent.ConcurrentHashMap; import java.util.function.Function; public class CustomCache<K, V> { private final ConcurrentHashMap<K, V> cache = new ConcurrentHashMap<>(); public V getOrDefault(K key, Function<? super K, ? extends V> mappingFunction) { return cache.computeIfAbsent(key, mappingFunction); } public void put(K key, V value) { cache.put(key, value); } } ``` In my unit tests, I simulate concurrent access by creating threads that both read from and write to the cache. Here’s how I set up the test: ```java import org.junit.jupiter.api.Test; import static org.junit.jupiter.api.Assertions.*; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; public class CustomCacheTest { private final CustomCache<Integer, String> cache = new CustomCache<>(); @Test public void testConcurrentAccess() throws InterruptedException { ExecutorService executor = Executors.newFixedThreadPool(10); for (int i = 0; i < 100; i++) { final int key = i; executor.submit(() -> { cache.put(key, "Value " + key); assertNotNull(cache.getOrDefault(key, k -> "Default")); }); } executor.shutdown(); executor.awaitTermination(1, TimeUnit.MINUTES); assertEquals("Value 99", cache.getOrDefault(99, k -> "Default")); } } ``` When I run this test, I sometimes get assertions failing, indicating that the value is not what I expected. It seems that some values are getting lost or overwritten. I have tried using `synchronized` blocks around my put and get operations, but that severely impacts performance. I'm unsure how to achieve both thread-safety and efficiency in this scenario. Has anyone dealt with a similar issue or could suggest best practices for implementing a thread-safe cache in Java? Any insights or suggestions would be greatly appreciated! I'm working on a service that needs to handle this. I'd really appreciate any guidance on this. This is my first time working with Java LTS. Any ideas how to fix this? I'm working in a Ubuntu 22.04 environment. What's the correct way to implement this?