Few Java Questions/Topics:

Java Super Object and its methods.
Difference between == and equals method, and their implementation.
What is hash?
What is thread, multi-threading, memory leak and how to prevent, load balancing, database indexing what it is?. Its significance, Connection pool, Virtualization.

HashMap, HashTable, HashSet, Map, Set,List, ArrayList, Arrays
Manipulate Strings,
Difference between List and ArrayList.
Stack, Queue, Heap, LinkedList, Priority

Data structure, algorithm.
OOP(abstraction, encapsulation, polymorphism, inheritance)

Project Management Tools and Few Technical terms

These are few terms, technologies or tools i used/heard/know so kept a record.

These are project management tools :

Openshift, Ansible, Docker, Kubernetes

JIRA, Confluence, Redmine, JOHO, Jenkins, FileZilla, Remmina, Team Viewer,
Sentry.io, Fabric,Wireframe,Balsamiq, Pencil, Owl Carousel(calender), Svg-Map

Ochawa, Branch(Branch.io),teamwork.

Deeplink, NextGen, SmartUrl (eg: bit.ly), localize, lokilise/lokalize.io, mparticle,, Circle CI, 

Technologies:-
React Android, React Java,

Technical terms:-
Virtualization, JMS, magical function, composer, connection pool, Hash,
Object class(Java), Thread Pool, load balancing, multiple system,Database indexing,

Infographics

Microservice Architecture - Introduction

Microservice is a service-based application development methodology. In this methodology, big applications will be divided into smallest independent service units. Microservice is the process of implementing Service-oriented Architecture (SOA) by dividing the entire application as a collection of interconnected services, where each service will serve only one business need.

For more information please visit :-

1. https://www.tutorialspoint.com/microservice_architecture/microservice_architecture_introduction.htm

2. https://www.edureka.co/blog/microservices-tutorial-with-example

Loose coupling and tight coupling in java – Comparison Example

In object oriented design, Coupling refers to the degree of direct knowledge that one element has of another. In other words, how often do changes in class A force related changes in class B.

Note : Tight coupling violets OPEN CLOSED PRINCIPLE ( A class should be open for extension and closed for modification).

You can read  open closed oops design principle .    Dependency Injection framework are also example of this, See more on this.


For more information please visit:-

1. http://www.interviewsansar.com/2018/03/24/loose-coupling-and-tight-coupling-in-java/

2. http://www.interviewsansar.com/2016/05/12/open-closed-principle-interview-question-with-awesome-answer/

3. https://www.geeksforgeeks.org/coupling-in-java/

4. https://dzone.com/articles/what-is-loose-coupling

5. http://www.codesuggestions.com/java/tight-coupling-and-loose-coupling-between-java-objects/

Big-O Notation

When trying to characterize an algorithm’s efficiency in terms of execution time, independent of any particular program or computer, it is important to quantify the number of operations or steps that the algorithm will require. If each of these steps is considered to be a basic unit of computation, then the execution time for an algorithm can be expressed as the number of steps required to solve the problem. Deciding on an appropriate basic unit of computation can be a complicated problem and will depend on how the algorithm is implemented.


For more information please go to this address :-

1. http://interactivepython.org/runestone/static/pythonds/AlgorithmAnalysis/BigONotation.html


2.http://pages.cs.wisc.edu/~vernon/cs367/notes/3.COMPLEXITY.html 

3. https://rob-bell.net/2009/06/a-beginners-guide-to-big-o-notation/

Data Structure and algorithm

Algorithms: Way of Solving well-specified computational problem.
                                                 OR
         Sequence of operation for solving a specific problem.


Euclid's Algorithm:
Used to find Greatest Common Divisor(GCD) of two positive integers.

Consider two positive integers m and n , m>n.
Step 1: Divide m by n, and let the remainder be r
Step 2: if r = 0 the algorithm ends, n is the GCD.
Step 3: If r is not 0 then, Set m = n; and n = r, go back to step1 and continue till, r = 0.

Note: This is a recursive algorithms as it calls over and over.

/**
     * This method takes two positive integers and finds their                                       * GreatestCommonFactor(GCD) using
     * Euclid's algorithm
     * @param a
     * @param b
     * @return
     */
public int greatestCommonFactor(int a, int b){
        if(b == 0) return a;
        return greatestCommonFactor(b, a%b);
}

Recursion Algorithm:

Merge Sort: A recursive algorithm for sorting large set of data.We merge two unsorted arrays.
This is a merge sort diagram and flow structure.

For more details :
https://www.hackerearth.com/practice/algorithms/sorting/merge-sort/tutorial/

Installing PostgreSQL and pgAdmin on Ubuntu

Installation Tutorial

Firstly install the database package:

$ sudo apt-get install postgresql

Now pgAdmin; a simple interface to manage your database:

$ sudo apt-get install pgadmin3 

Once the installation has finished, it's time to set up a password for the main account; you'll log in to postgresql:

-->> The version of postgres may vary slightly depending upon the Ubuntu version

$ sudo -u postgres psql postgres
psql (9.1.10)
Type "help" for help.

And then type \password postgres, and you'll be prompted for your password:

postgres=# \password postgres

Then write your password in. (If you can't see what you type, it's ok, this is for security reasons). Now type \q to exit postgres command-line interface:

postgres=# \q

Install Server Instrumentation
It's a package containing extra tools that help you manage your database. It's pretty much commonplace so I suggest you install it:

$ sudo apt-get install postgresql-contrib

Running pgAdmin

When you first open pgAdmin, you must Register a new Server (i.e.,create a new connection):
Some information will have been filled out for you. Set "localhost" as host, choose a name for your server, write "postgres" as username and write the password you've set in the previous steps for password:

References

• Official ubuntu docs on PostgreSQL

For to install latest version of pgadmin4X...

https://askubuntu.com/questions/831262/how-to-install-pgadmin-4-in-desktop-mode-on-ubuntu/844429