Apache Maven for Beginners
Install Oracle JDK 12 on Linux
Apache Spark Tutorial
Install Ballerina on Linux
Complex Event Processing - An Introduction
Smelly instanceof Operator

Smelly instanceof Operator

The instanceof operator in Java is used to check if a given reference is an instance of (aka object of) a given class. Though it is useful in some situations, it is a bad practice to use the instanceof operator. Whenever I see instanceof in my student's projects or a code review I raise the alarm. This article explains why the instanceof operator is considered a bad practice and how to avoid it.
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Resume Tips for Software Engineers

Years ago as an international student preparing my resume to get my first job in Canada, I had a lot of questions and I did search a lot on how to make a resume that fits Canadian employer's requirements and style. Things have changed. Eventually, I got offers from some high tech companies and landed in a good job and now I am interviewing candidates who are like I was a couple of years ago. After looking at more and more resumes, I decided to share my experience here with a hope that will make someone's life better.

For whom this article is for? Well! for anyone looking for a new job in Canada. Especially if you are  new immigrant who has no idea about what Canadian employers are looking for, this article is tailored to your requirements. Though my experience is limited to Canada the companies I applied for are mostly US-based companies so I hope it can be applied anywhere in North America. This article is targeting only those who are in the software industry. I don't know how much it will overlap with other industries. The rest of the article is divided into two topics: 1. Resume Sections, 2. Resume Format. The first topic covers what to include and not to include in your resume and the second topic provides some formatting tips to make your resume get you a call from the recruiter.
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Presto SQL: Join Algorithms

Presto is a distributed big data SQL engine initially developed by Facebook and later open-sourced and being led by the community. The last article Presto SQL: Types of Joins covers the fundamentals of join operators available in Presto and how they can be used in SQL queries. With that knowledge, you can now learn the internals of Presto and how it executes join operations internally. This article presents how Presto executes join operations and the algorithms used to join tables.

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Presto SQL: Types of Joins

SQL Join is one of the most important and expensive SQL operation and require deep understanding from database engineers to write efficient SQL queries. From database engineers' perspective, understanding how join operation works help them to optimize them for efficient execution. This article, explains the join operations supported in the open source distributed computing engine: Presto SQL. This article is based on now archived prestodb.rocks blog which I referred to learn the Join algorithms of Presto.

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Read Carbondata Table from Apache Hive

Apache Carbondata an indexed columnar data store heavily depends on Apache Spark but also supports other Big Data frameworks like Apache Hive and Presto. This article explains how to read a Carbondata table created in Apache Spark from Apache Hive in two sections: 1. How to create a table in HDFS using Apache Spark, 2. How to read the Carbondata table from Apache Hive.

Read Carbondata Table from Apache Hive
  • Oracle JDK 1.8
  • Apache Spark
  • Apache Hadoop (Carbondata officially support Hive 2.x. In this article, Apache Hadoop 2.7.7 is used)
  • Apache Hive (Carbondata officially support Hive 2.x. So better to stick to 2.x version. In this article, Apache Hive 2.3.6 is used to demonstrate the integration)
  • Carbondata libraries
Please follow the Integrate Carbondata with Apache Spark Shell article to compile Carbondata from source and integrate it with Apache Spark. This article is written based on the assumption that you have already followed all the steps from the above-mentioned article.

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Integrate Carbondata with Apache Spark Shell

Apache Carbondata an indexed columnar data store solution for fast analytics on big data platform, e.g.Apache Hadoop, Apache Spark, etc. This article is written to provide a quick start guide on how to integrate Carbondata with Apache Spark Shell. Why another article while there is a quick start guide on the official website? Things are not always as smooth as expected. In my experience, integrating Carbondata with Apache Spark using pre-built binaries didn't work as expected. So here is the quick start tutorial.

Integrate Carbondata with Apache Spark Shell
Carbondata requires Java 1.7 or 1.8 to run and Apache Maven to build from source. Please make sure that you have Oracle JDK 1.8, supporting Apache Maven and Git to setup Carbondata. If you don't have Oracle JDK or Apache Maven installed in your system, please follow the given links below to install them first.

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Install the latest Oracle JDK on Linux

Even though OpenJDK is available in Linux repositories, some applications strictly require Oracle Java Development Kit. This article shows you how to manually install Oracle JDK 13 on your Linux system. This article uses JDK 13$java_update_no to demonstrate the installation. In the provided commands, replace the version specific paths and file names according to your downloaded version.
Oracle provides deb and rpm installers
If your Linux distribution is using DEB package format like Debian, you can download and install the $java_version$java_update_no_linux-x64_bin.deb file using the following command:
sudo dpkg -i $java_version$java_update_no_linux-x64_bin.deb
If your  Linux distribution is using RPM package format like Cent OS, you can download and install the $java_version$java_update_no_linux-x64_bin.rpm file using the following command:
sudo rpm -ivh $java_version$java_update_no_linux-x64_bin.rpm

However, this article explains the manual installation method which is applicable for all Linux distributions out there. Personally, I prefer the manual installation because I have more control over the changes made in the system.

Install Oracle JDK 13 on Linux

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Install MySQL 8 on Ubuntu/Linux Mint

Ubuntu official software repository provides MySQL 5.x which can be installed by following the article: Install MySQL with phpMyAdmin on Ubuntu. However the latest release of MySQL: 8.x, requires you to manually add the software repository into your system which makes the installation process little tricky. This article walks you through the end-to-end installation process of MySQL 8.

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Android: List External Storage Files

This article explains how to list files from the external storage (SD Card) in Android. Though you can list files recursively using a simple method, the new Runtime Permission Model introduced in Android 6 makes it a little difficult. Let's dive into the code and see how we can list all the files recursively.

Android: List External Storage Files

As I mentioned earlier, I am using Kotlin for Android development since it is the future of Android. If you are using Java, just copy and paste the code into your class method by method. The Android Studio will translate the method into Java for you.
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ANTLR Hello World! - Arithmetic Expression Parser

ANTLR Hello World! - Arithmetic Expression Parser

Ever wondered how all these programming languages understand what you write? This article reveals the truth: Language Parsing. It is often referred to as parsing, syntax analysis, or syntactic analysis. Regardless of the term, it is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The following diagram depicts the language parsing process:

Language Parser

As you can see, the Language Parser (which is part of the compiler) takes an input (which is the source code), validates it against the Language Grammar and produces an Abstract Syntax Tree (commonly known as AST which is representing the source code in a tree structure).

ANTLR (ANother Tool for Language Recognition) is a tool to define such grammar and to build a parser automatically using that grammar. It also provides two high-level design patterns to analyze the AST: Visitor and Listener. ANTLR is being used by several languages and frameworks including Ballerina, Siddhi, and Presto SQL. This article introduces ANTLR to you using a hello world application to evaluate basic mathematical expressions as a string.

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Install the latest Eclipse on Linux

This article shows you the way to install the latest version of Eclipse on Linux. There are other ways to install Eclipse using scripts to automate the installation. However, I prefer the manual installation method explained in this article so that you know where your files go. Later if you want to remove the Eclipse, it is just two commands as explained at the end of the article.

If you do not have Java in your system, follow this link and install the Java first.

Step 1:
Download the desired version of Eclipse from the official site:

Step 2:
Open the Terminal (Ctrl + Alt + T) and enter the following command to change the directory.
cd /opt

Step 3:
Enter the command given below to extract the Eclipse from ~/Downloads directory. If your downloaded file is in any other directory, replace the last parameter by the actual file path.
sudo tar -xvzf ~/Downloads/eclipse-jee-2019-12-R-linux-gtk-x86_64.tar.gz

Step 4:
Open another Terminal (Ctrl + Alt + T) and enter the following command to create a shortcut file for eclipse.
gedit eclipse.desktop

Step 5:
In the opened gedit, copy and paste the following text.
[Desktop Entry]
Comment=Integrated Development Environment

Step 6:
Save and close the gedit.

Step 7:
Enter the following command in the terminal to install the shortcut.
sudo desktop-file-install eclipse.desktop

Now search for Eclipse in the dashboard and open it.

Upgrade Eclipse

If you have already installed Eclipse using the above method and would like to upgrade the Eclipse to the latest version, just remove the Eclipse from /opt director and follow Steps 1 to 3 from the installation process.
sudo rm -rf /opt/eclipse

Remove Eclipse

Removing the Eclipse installed as described in this article is just two lines of commands.

Step 1:
First, remove the menu entry you created in Step 7.
sudo rm /usr/share/applications/eclipse.desktop

Step 2:
Delete the /opt/eclipse folder.
sudo rm -rf /opt/eclipse

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Javalin: A Tiny but Mighty Framework

Two years ago, I wrote an article Microservices in a minute using the open source framework MSF4J. Today I came across another framework Javalin: another lightweight framework to develop lightweight web applications with less or no effort. We already have plenty of web frameworks including the shining star Spring. What makes Javalin different is its simplicity. In addition, it can be used as a microservice framework or a tiny web framework to serve a web application with static files. In Javalin developers' words:

Javalin’s main goals are simplicity, a great developer experience, and first-class interoperability between Kotlin and Java.

Comparing Javalin with Spring is like comparing a shaving blade with a Wenger 16999 Swiss Army Knife Giant, but it does what it is supposed to do. If you want to quickly add a REST endpoint for a quick demo or if you just need a simple web framework without any additional gimmicks like Dependency Injection or Object Relational Mapping, consider Javalin. It is easy to learn and lighter to run.

In this article, you will see how to use Javalin as a web framework to serve a contact-us page and how to build a CRUD micro-service using Javalin.


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Serve TensorFlow Models in Java

TensorFlow is a famous machine learning framework from Google and a must to know asset for machine learning engineers. Even though Python is recommended to build TensorFlow models, Google offers Java API to use TensorFlow in Java. Still, Python is the easiest language to build TensorFlow models, even for Java developers (learn Python, my friend). However, enterprise applications developed in Java may require the artificial intelligence offered by a trained TensorFlow model. In this article, you will learn how to load and use a simple TensorFlow model exported from Python.

Serve TensorFlow Models in Java
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