Looking back on my 2021

As of this writing, the COVID-19 pandemic still persists. In Vietnam, people have just passed a horrible time of lockdown, we needed to stay at home for nearly 4 months. I have even got covid infected and spent a quarantine time for more than three weeks.

My balcony garden

Tech Lead at UMB Solution (ubitec)

Tech Lead was my official job title at ubitec. I have worked closely with two teams (7 developers in total) for developing two products ubichat and ubibot. My responsibilities were divided into three following roles:

- Software engineer: joined teams to implement/solve several challenging problems

- Technical consultant: for developers, Product Owners, Product Managers, and customers.

- Mentor: grew the teams in both technical skills and soft skills

Mental care

In my spare time, I enjoyed reading books and watching videos. I have been doing "meditation" in ... every moment in my life (no kidding 😊)

The following was my favorite 2021 Youtube channels:

- The Quoc Khanh Show Premium (TQKS Premium)

- Bar stories - Dustin On The Go

- Johnny Trí Nguyễn

Making life easier

This was a tough year due to COVID, however fortunately I could get my car driving license and buy a new house.

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Happy new year, 2022!

Comments

Multiple Inheritance of State and Implementation

Today, I was just curious about why an enum can not extend anything else. I took a look on the Oracle document here , and I found the answer is below: "All enums implicitly extend java.lang.Enum. Because a class can only extend one parent (see Declaring Classes), the Java language does not support multiple inheritance of state (see Multiple Inheritance of State, Implementation, and Type), and therefore an enum cannot extend anything else." I have been learned of it before. But, wait a sec...! Why Java does not support multiple inheritance of state? Since I have worked with other programming languages like C++, I was able to make a class extend some other classes. The short answer is to avoid the issues of multiple inheritance of state . I wonder if other programming languages have these below terms but Java does. Multiple inheritance of state It is the ability to inherit fields from multiple classes. There is a problem and Java avoids it. "For exa...

Performance of a Data Structure

Why data structures matter The fact is that programs are all about processing data. Data structures are referred to how data is organized which affects the time of executing a program. How to measure the performance of a data structure In order to measure "how fast"/efficiency/performance of a data structure, we measure the performance of its operations. There are four basic operations including reading , searching , insertion , and deletion . A pure time consuming is not used for the measuring because it is not reliable depending on the hardware that it is run on. But instead, we use the term time complexity which refers to how many steps an operation takes. An example of how a single rule can affect efficiency Let's compare two data structures: Array and Set (with N elements). 1. Array - Reading : 1 step (because the computer has the ability to jump to any particular index in the array) - Searching : N steps (the worst case with linear search) - Inserti...

Using Drools to Dynamically Manipulate Metadata of JSF Components

The post is just an approach to change metadata (e.g maxlength, required, etc) of JSF components (e.g. inputText, selectOneMenue, etc) by Drools. Project structure Tools being used Java version 1.8.0_131 Apache Maven 3.5.0 Apache Tomcat 8.0.16 Don't forget to configure your confidential information on these following files: pom.xml, settings.xml (Maven) and tomcat-users.xml (Tomcat). For example: Source code https://github.com/vnnvanhuong/java_lab/tree/master/jsfdrools

Monday vhandit #2

Introduction to OpenLDAP directory service "A directory is a specialized database specially designed for searching and browsing, in addition to supporting basic lookup and update functions" A directory service can be local, providing a restricted context; or global, providing service to a much broader context. Curlie is a good example of a directory service. LDAP (Lightweight Directory Access Protocol) is a protocol for accessing directory services , specifically X.500-based directory services. OpenLDAP is an open-source implementation of LDAP. Writing system software: code comments I have read Clean Code (by Uncle Bob) and I thought that I should void comments since the code it explains its implementation itself. That is right but not always true. In this post, the author categorized the comments into 9 types. Only "trivial comments" and "backup comments" are the ones that should be avoided. I myself agree with "writing good comments is harder tha...

Regex - Check a text without special characters but German, French

Special characters such as square brackets ([ ]) can cause an exception " java.util.regex.PatternSyntaxException " or something like this if we don't handle them correctly. I had met this issue. In my case, my customers want our application should allow some characters in German and French even not allow some special characters. The solution is that we limit the allowed characters by showing the validation message on GUI. For an instance, the message looks like the following: "This field can't contain any special characters; only letters, numbers, underscores (_), spaces and single quotes (') are allowed." I used Regular Expression to check it. For entering Germany and French, I actually don't have this type of keyboard, so I referred these sites: * German characters: http://german.typeit.org/ * French characters: http://french.typeit.org/ Here is my code: package vn.nvanhuong.practice; import java.util.regex.Matcher; import java.util...

vhandit

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