Release Notes

Tag: java

Drools

Published by Kaustubh Saha on September 24th, 2019

Drools is a Java-based business rule management system (BRMS) based on an enhanced implementation of a the Rete algorithm (a pattern matching algorithm developed to efficiently control triggering of rules). KIE (Knowledge Is Everything) is the new umbr...

Getting started with JIRA REST API

Published by Kaustubh Saha on February 26th, 2019

JIRA allows programmatic access to data through it's Java based REST API. Essentially every call to the Java API translates to an HTTP request to the JIRA REST Services. The JIRA REST API uses JSON as its communication format, and the standard HTTP me...

Java Memory Model

Published by Kaustubh Saha on January 10th, 2019

The Java memory model describes how threads in the Java programming language interact through memory. Together with the description of single-threaded execution of code, the memory model provides the semantics of the Java programming language.In single...

Spring : creating unique beans per thread

Published by Kaustubh Saha on January 10th, 2019

In stand-alone non-web Java applications, using Spring, the most commonly used bean scopes are singleton and prototype. If a bean scope is set to singleton (and by default bean scope is always singleton), the Spring container creates exactly one instan...

False Sharing

Published by Kaustubh Saha on January 10th, 2019

Most modern day computer architectures have a tiered memory structure. Cache memory is really fast (SRAM) and is also physically located very close to the processor (L1 is placed on CPU chip closest to processor, L2 is placed in between CPU and RAM, i...

ConcurrentHashMap

Published by Kaustubh Saha on December 31st, 2018

A ConcurrentHashMap is a thread safe implementation of a hash table data structure. A ConcurrentHashMap has the same functional specifications as HashTable with the performance benchmarks comparable to a HashMap. Before we look into ConcurrentHashMap's...

Transfer Queue

Published by Kaustubh Saha on December 31st, 2018

A transfer queue is a special type of BlockingQueue (it implements BlockingQueue) where producers may optionally wait until consumers have consumed the corresponding element. Like other blocking queues, a TransferQueue may be capacity bounded. If so, ...

Common inter thread communication problems

Published by Kaustubh Saha on December 30th, 2018

Sleeping Barber Problem In computer science, the sleeping barber problem is a classic inter-process communication and synchronization problem between multiple operating system processes. The analogy is based upon a hypothetical barber shop with one bar...

Hardware Based Locking

Published by Kaustubh Saha on December 29th, 2018

CAS (Compare And Swap) : CAS ( Compare And Swap) is an atomic instruction used to implement optimistic locking. It compares the contents of a memory location with a given value and, only if they are the same, modifies the contents of that memory locati...

Executor Framework in Java

Published by Kaustubh Saha on December 28th, 2018

Executor is a framework provided by the JDK (starting 1.5) which simplifies the execution of tasks in asynchronous mode. At a high level, the Executor classes provide abstraction for assigning tasks to a pool of threads. The java.util.concurrent packag...

Synchronization tools for coordinating between threads

Published by Kaustubh Saha on December 27th, 2018

Apart from the low level synchronization abstractions (synchronized/Lock/Semaphore), Java also provides a bunch of high level abstractions for synchronizing activities of two or more threads. Let's have a closer look at some of them CountdownLatch Coun...

Reflection and String immutability

Published by Kaustubh Saha on December 26th, 2018

One very powerful but risky tool is Reflection. Using reflection, you can break almost everything - from encapsulation to immutability Here is a piece of code which breaks immutability of String class import java.lang.reflect.Field; public class Muta...

ThreadLocal

Published by Kaustubh Saha on December 25th, 2018

The ThreadLocal class helps us maintain 'per thread' semantics. Thus, even if two threads are executing the same code, and the code has a reference to a ThreadLocal variable, then the two threads cannot see each other's values. This is especially helpf...

Special thread features

Published by Kaustubh Saha on December 24th, 2018

Shutdown Hook : Shutdown Hooks are pre-registered (but yet-to-be-started) threads which are run by JVM when an application is shutting down. There can be more that one shutdown hooks registered with a JVM, JVM does not give any guarantee on the order i...

Points to consider while working on multithreaded code

Published by Kaustubh Saha on December 23rd, 2018

In general, there are 4 main points to consider when it comes to dealing with multithreaded code : mutual exclusion caching reordering happens-before Let's examine each of them in detail : Mutual Exclusion : Mutual Exclusion essentially means that only...

Common concurrency problems

Published by Kaustubh Saha on December 20th, 2018

Starvation Starvation refers to a situation where a thread is unable to make any progress (or progressing very slowly) despite being in runnable state. Some of the common causes of starvation are : Other 'greedy' threads with higher priority are hogg...

Threads and Processes

Published by Kaustubh Saha on December 15th, 2018

What is a thread ? A thread is a kernel abstraction for scheduling work on the CPU. A thread is essentially an execution context which a CPU needs to execute a bunch of instructions. As a bare minimum coding construct, any thread implementation will ha...