vmlens BlogEach method of ConcurrentHashMap is thread-safe. But calling multiple methods from ConcurrentHashMap for the same key leads to race conditions. And calling the same method from ConcurrentHashMap recursively for different keys leads to deadlocks. Full Article...
When writing thread-safe classes the main issue is to separate the data into multiple independent parts. And to choose the right size for those parts. If the part is too small our class is not thread-safe. If the part is too large the class is not scalable. Full Article...
There exist multiple queue implementations in Java. Six alone implementations in the package java.util.concurrent. Why are there so many implementations? For a data structure that is implemented in the single-threaded case as a linked list? Full Article...
java.util.concurrent.atomic.AtomicReference is a class designed to update variables in a thread-safe way. Why do we need the class AtomicReference? Why can we not simply use a volatile variable? And how to use it correctly? Full Article...
Tests for thread safety differ from typical single-threaded tests. To test if a method is thread-safe we need to call the method in parallel from multiple threads. We need to do this for all potential thread interleavings. And afterward, we need to check if the result is correct. Full Article...
Thread safety in java means that the methods of a class are either atomic or quiescent. So what does atomic and what does quiescent mean? And why are there no other types of thread-safe methods in java? Full Article...
Copy on write is a technique which allows you to update a data structure in a thread-safe way. The main advantage of copy on write is that reading threads get never blocked. Why do we need this technique? And how to use this technique correctly? Full Article...
AtomicInteger is a class specially designed to update integers in a thread-safe way. Why do we need this a class? Why can we not simply use a volatile int? And how to use AtomicInteger? Full Article...
Combining dependent thread-safe methods leads to race conditions. Only when the methods do not depend on each other, we can combine them in a thread-safe way. Why is combining thread-safe methods an error? Full Article...
The more I learn about multi-threaded programming, the harder it gets. Coordinating multiple threads modifying the same data is complicated. The java.util.concurrent.ConcurrentHashMap for example needs with 4264 lines of code two times more lines of code than its single threaded counter part the java.uti.HashMap with 1617 lines of code. So I think the best solution for concurrent programming is to avoid shared state. Full Article...
What fascinates me about the volatile keyword is that it is necessary because my software still runs on a silicon chip. Even if my application runs in the cloud on a virtual machine in the Java virtual machine. But despite all of those software layers abstracting away the underlying hardware, the volatile keyword is still needed because of the cache of the processor my software runs on. Full Article...
© 2020 vmlens Legal Notice Privacy Policy
vmlens