Bad String abuse

By
In this Java Puzzler, it has some serious abuse of Strings, but what is going on?

https://vanilla-java.github.io/2016/04/21/Bad-String.html

Comments

  1. kontiky30 April 2016 at 18:20

    Thank you for the puzzle!

    Unfortunately, I couldn't clearly understand the source of such behaviour. I suppose the the reason is in a way how String Constant Pool selects constants on a base of hashCode() execution. But I'm not sure.

    So will wait for your solution :)

    P.S. could you, please, allow comments and RSS subscription on your GitHub blog?

    ReplyDelete
    Replies
    1. kontiky30 April 2016 at 18:33

      I read that internally String Constant Pool uses Hashtable for storing strings. So looks like equal hashCode() values isn't enough for getting puzzle effect. Also, at the first sight, external synchs on "bb" and "cC" really work on String instance wrappers not on internally char[] arrays...

      So the puzzle is really puzzle :)

      Delete

Post a Comment

Popular posts from this blog

Java is Very Fast, If You Don’t Create Many Objects

By
Image
  You still have to watch how many objects you create. This article looks at a benchmark passing events over TCP/IP at 4 billion events per minute using the net.openhft.chronicle.wire.channel package in Chronicle Wire and why we still avoid object allocations..  One of the key optimisations is creating almost no garbage. Allocation is a very cheap operation and collection of very short-lived objects is also very cheap. Does this really make a difference? What difference does one small object per event (44 bytes) make to the performance in a throughput test where GC pauses are amortised? While allocation is as efficient as possible, it doesn’t avoid the memory pressure on the L1/L2 caches of your CPUs and when many cores are busy, they are contending for memory in the shared L3 cache.  Results Benchmark on a Ryzen 5950X with Ubuntu 22.10. JVM Vendor, Version No objects Throughput, Average Latency* One object per event Throughput, Average Latency* Azul Zulu 1.8.0_322 60.6 M event/s, 528
Read more

Low Latency Microservices, A Retrospective

By
  I wrote an article on  low latency microservices   almost five years ago now. Chronicle Software has worked with a number of tier-one investment banks to implement and support those systems. What has changed in that time and what lessons have we learnt? Read this article and learn what we learned after five years of developing and supporting low latency microservices. Separation of Concerns Give Better Testability Microservices repeatedly demonstrated that testing and debugging business components were much easier with simple, stand-alone components with clear contracts between microservices. Unit tests were still used to start with. However, in 2017 we moved almost entirely to behavior-driven development of microservices. Unit tests are still used for lower-level libraries and utilities. As our microservices are all based on  Kappa Architecture , all our behaviour driven tests are modeled as a series of events in and out of the service. An input test might look like this --- oms : O
Read more

Unusual Java: StackTrace Extends Throwable

By
Image
There are things you can do in Java you rarely see, generally because there is no use for it. However, there are some unusual things in Java that could be surprisingly useful. Chronicle Software uses a number of different usual patterns in it’s low-level libraries most developers wouldn’t generally come across. One of them is a class that extends Throwable but isn’t an Error or an Exception. StackTrace Extends Throwable package net.openhft.chronicle.core; /** * Throwable created purely for the purposes of reporting a stack trace. * This is not an Error or an Exception and is not expected to be thrown or caught. */ public class StackTrace extends Throwable {     public StackTrace() { this ( "stack trace" ); }     public StackTrace(String message) { this (message, null ); }     public StackTrace(String message, Throwable cause) {         super (message + " on " + Thread. currentThread ().getName(), cause);    }     public static StackTrace forThread(Thread t) {       
Read more