With all the hype and buzz surrounding NoSQL, I decided to have a look at it. I quickly found that there is not one NoSQL I could learn. Rather, there are various different solutions with different purposes and trade offs. Those various solutions tend to have one thing in common: processing of data in NoSQL storage is usually done using MapReduce framework. Search on MapReduce found various scatte
I have been reading on Join implementations available for Hadoop for past few days. In this post I recap some techniques I learnt during the process. The joins can be done at both Map side and Join side according to the nature of data sets of to be joined. Reduce Side Join Let’s take the following tables containing employee and department data. Let’s see how join query below can be achieved using
In the last few month we’ve went through this decision making process: which technology stack to choose for enterprise development on the Java platform? There are various alternatives. However, the ones we’ve discussed intensively were: Pure Java EE 6 Stack vs. Spring with Java EE. The following blog article summarizes key issues I found interesting when you consider one of those technology stack
In any programming language that combines subtype polymorphism (object orientation) with parametric polymorphism (generics), the question ofvariance arises. Suppose I have a list of strings, type List<String>. Can I pass that to a function which accepts List<Object>? Let’s start with this definition: interface List<T> { void add(T element); Iterator<T> iterator(); ... } Broken covarianceIntuitivel
IntroductionJava EE has a number of APIs and constructs to support Asynchronous execution. This is vital from a scalability and performance stand point. Let us assume 2 modules which are interacting with each other. When moduleA (the sender) sends a message to moduleB (the receiver) in a Synchronous fashion, the communication takes place in the context of a Single thread i.e. the thread which init
Java time basicsjava.util.Datejava.util.Date is definitely the most common time-related class. It represents a fixed point in time, expressed as the relative number of milliseconds elapsed since epoch. java.util.Date is time zone independent, except for the toString method which uses a the local time zone for generating a String representation. java.util.CalendarThe java.util.Calendar is both a Da
EDITORIAL NOTE: In this post, we feature a comprehensive Java Annotations Tutorial. Annotations in Java are a major feature and every Java developer should know how to utilize them. We have provided an abundance of tutorials here at Java Code Geeks, like Creating Your Own Java Annotations, Java Annotations Tutorial with Custom Annotation and Java Annotations: Explored & Explained. We also featured
Jakub HolySeptember 23rd, 2012Last Updated: October 22nd, 2012 VisualVM is a great tool for monitoring JVM (5.0+) regarding memory usage, threads, GC, MBeans etc. Let’s see how to use it over SSH to monitor (or even profile, using its sampler) a remote JVM either with JMX or without it. This post is based on Sun JVM 1.6 running on Ubuntu 10 and VisualVM 1.3.3. 1. Communication: JStatD vs. JMX Ther
Recently, I had a chance to present the subject at the local IT community meetup. Here is the basic presentation: Java Code Quality Tools and more meaningful mind map: But, I think I need to cover this subject more deeply. This blog post should be something like start point for further investigation in this direction. 1. CodePro Analytix It’s a great tool (Eclipse plugin) for improving software qu
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