Sat. Jun 15th, 2024
Skills of Java Developer

More than 3 billion devices in the world run on Java. You can find Java everywhere – on websites, in games, in apps, in scientific research, in a smart house, and in a Tesla car.

Whether you live in India or any other country in the world, you have definitely used products written in Java. So an Indian Java developer will definitely have a job.

  1. The English Language

Why it matters:

  • All documentation is written in English.
  • Working for an international company, all meetings and calls will be in English. Therefore you need to have at least an elementary or beginner level. Many companies have courses in English, but these courses (for example, on are designed to increase your skills, not to start from scratch.
  1. Git

What you need to know:

  • git clone
  • git pull
  • git commit
  • git push
  • gist stash
  1. Operating System

Decide on the operating system you wish to work with. You will have to write scripts to automate the operations: bash scripts on Linux, and bat scripts on Windows.

  1. Algorithms and Data Structures

What you need to know:

  • Sorting algorithms.
  • How to work with trees.
  • Understand lists, queues, and stack.
  • Sorts: bubble sort, merge sort, and so on.
  • Search algorithms.
  • Mathematics: how to count arithmetic mean, geometric mean, etc.
  1. Java Core

Java Core is a programming language base that includes data structures, syntax, and everything else.

Java Basic

  • Basic syntax.
  • OOP.
  • Generic classes – template classes that adjust to what you need; store and handle whatever data types you specify when you declare them.
  • Strings. Understand how to do pattern matching, searching in strings, etc.
  • Collections to store data: Map, List, Array, Set (often asked in interviews).


  • Thread.
  • Thread Pool.
  • Multithreaded application patterns.

Java 8 Features

  • Lambda-functions (anonymous functions).
  • Stream.
  • Class Optional.
  • Functional programming, etc.


  • Understanding how to work with files.
  • Networking (Socket).
  • Java NIO/NIO2 (often found in jobs).
  1. Tools

Fluent in their IDE (Eclipse, IDEA, VSCode, vim) and understand how to create applications from scratch, how to build applications, what plugins to install, use shortcuts, etc.

Build (builders)

  • Maven – uses XML to describe the project.
  • Gradle – uses the groovy programming language to describe the project.


  • Docker Compose.
  • Docker swarm.
  • Kubernetes.


Jenkins allows you to set up continuous integration, testing, and publishing your applications.

  1. Frameworks and Libraries

For the backend

  • Spring: Spring Core (a framework for creating services), Spring Data (working with the database), Spring cloud (working with microservices), Spring Security (protecting applications).
  • Hibernate – to work with the database.
  • Quarkus and Micronaut – allow you to write reactive applications quickly.
  • Vert.x – asynchronous web framework.

For desktop

  • JavaFX, Swing, AWT – to create GUI in hours.
  • Web basic (for full-stack development)
  • JavaScript: Angular, Vue.js, or React.
  • HTML5.
  • Bootstrap.
  1. Testing

Unit Testing is testing the functionality of your program. When you know what the output should be, you submit a method, and the tests compare whether the method succeeded or failed and got the expected result.

  • Junit, Mockito libraries for testing database actions.
  • Auto Testing – Selenium lets you create browser windows, go to a web page, test clicks, input fields, etc.
  • Integration Test tests how the application integrates into the infrastructure and how it works in it. Scripting libraries used: Selenium, Robot.
  1. Utils

Deeper into optimizing the process of work and development:

  • Log4j, SLF4j (logging) – tracks client actions.
  • JavaDoc – describes classes and later generates .html or .pdf documentation from that.

Java Analyze

Utilities that help to understand where an error has occurred:

  • Heap Analyzer.
  • Thread Dump Analyzer.

Java Analyze

  • Jira for task tracking.
  • GitLab, GitHub, BitBucked – you need to know how to use services to store source code.
  • AWS – it is important to know what microservices are, how microservices are deployed, etc.
  • HTTP – Postman application generating requests to servers.
  1. Databases
  • SQL – DML (data manipulation language), DCL (language gives access to certain databases and tables), TCL (transaction processing), DDL (data definition language).
  • How to connect to the database using the JBDC driver.
  • Hibernate.
  • NOSQL.
  • MySQL.
  • MSSQL.
  • PostgreSQL.
  • MongoDB.
  • ClickHouse.
  1. Application Optimization
  • JMH
  • JIT
  • warmup
  • JVM (OpenJDK, AdoptOpenJDK, Zulu, GraalVm)

12. Where to Grow Up

  • Manager – work with people.
  • Architect – to think through application workflows.
  • Product Owner – to combine development and management.

Why Learn Java?

Java is the only language that can run code written 25 years ago in its latest version. That’s why it’s highly valued in the IT world.

Top 6 reasons why millions of developers started learning Java and fell in love with it:

  • Security. In Java, you can account for all bugs and crashes and repair the application in case of malfunctions.
  • Maturity. Java has been around for 25 years. During that time, a vast system formed around the language, with people sharing their experiences and knowledge. The older the language, the more widely used it becomes. That’s why it’s very easy to find a job as Java-dev.
  • Write Once Run Anywhere. The same code can be run on different devices – computers, mobile devices, and game consoles.
  • Performance. Java applications are fast, so they’re often used in finance.
  • Free tools. The java platform and many development environments are free for developers. Therefore, Java is suitable for novice programmers and small companies.
  • Outlook. Every six months, there is new functionality in Java. It expands the possibilities for developers.