Learning path

Java Developer Roadmap

What to learn for a Java job, in the order to learn it: the language through generics and design patterns, the command line, Git and SQL, then the data structures and algorithms Java interviews are built on, and finally code a team can maintain. Free, hands-on, in your browser, with nothing to install.

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471,255+ codders enrolled across these courses

599 lessons577 challenges2,792 quiz questions

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13 free certificates along the path

The Java developer roadmap, step by step

17 courses6 sections599 lessons577 challenges2,792 quiz questions

Each step is made of existing Coddy courses, and every Start button opens them in Java. Take the steps in order, or start with the one you are missing; progress is saved per course.

1
Step 1
Java, from syntax to design patternsDedicated page
Start this stepStartThree sections. Fundamentals covers types, operators, loops, methods, arrays and strings; Logic & Flow adds multi-dimensional arrays, HashMap, HashSet, exceptions, StringBuilder, regular expressions and dates with java.time; Object Oriented Programming covers encapsulation, inheritance, interfaces, abstract classes, generics, records and the classic design patterns, ending in a library management project. The hard part at first is Java's ceremony, a class and a type on everything; learn it deeply anyway, because the Java you will read at work is layer after layer of interfaces and classes.Start Dedicated page
3 sections, in order
219 lessons288 challenges1,464 questions
2
Step 2
Linux and the command lineDedicated page
Start this stepStartPaths, files, wildcards, grep, pipes and redirection, permissions, environment variables and shell scripts. Java services run on Linux servers and in containers, Maven and Gradle run from a terminal, and when a service fails in production, the first move is to grep its log for the stack trace. JAVA_HOME and PATH are the first environment variables a Java setup asks you to get right.Start Dedicated page82 lessons68 challenges440 questions
3
Step 3
Git and version controlDedicated page
Start this stepStartStaging, commits, .gitignore, branches, merges and conflicts, undoing mistakes and working with remotes. Java teams share large, long-lived codebases through branches and pull requests, and the files everyone edits, pom.xml or build.gradle, are where branches tend to collide. Keep target/ and build/ out of your commits from the first day.Start Dedicated page58 lessons46 challenges370 questions
4
Step 4
SQL fundamentalsDedicated page
Start this stepStartFiltering, sorting, joins, grouping, aggregates, subqueries, WITH clauses and window functions, run against real tables. Java backends reach relational databases through JDBC, JPA and Hibernate, and an ORM hides SQL only until a page gets slow; then you read the queries it generated and spot the N+1 problem, one query per row where a single join would do.Start Dedicated page72 lessons72 challenges360 questions
5
Step 5
Data structures, built by hand
Start this stepStartStack, queue, linked list, binary tree and hash table, each written from scratch in Java and then used to solve problems. The Java course teaches you to override equals() and hashCode(); building a hash table shows why the two must agree, and why a HashMap key whose hash changes after insertion can no longer be found.Start
5 courses, in order
66 lessons34 challenges
6
Step 6
Algorithms and recursive thinking
Start this stepStartRecursion challenges, then bubble, selection, insertion, merge and quick sort in Java, with the sorts animated in Coddy's algorithm visualizer. Java sets a practical limit on recursion: the JVM does not eliminate tail calls, so a deep enough recursion throws StackOverflowError, and this step is where you learn when a loop is the better tool.Start
6 courses, in order
62 lessons37 challenges158 questions
7
Step 7
Code other people can read
Start this stepStartAn object-oriented project built end to end and a bank of coding problems, both in Java. Readable Java is what code review on a large team actually checks: names that say what a class is for, methods that do one thing, no class that knows everything.Start
2 courses, in order
1. User Class - OOP Project8 lessons1 challenges
2. Coding Problems32 lessons31 challenges
40 lessons32 challenges

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1const greeting = "Hello, Coddy!"

2function sayHi(name) {

3 return greeting + " " + name

Test #1

Test #2

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"Alex"

Output

"Hello, Coddy! Alex"

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Read, listen, test yourself, ask the AI, or look up anything you've already covered. Every lesson meets you where you are.

Intro to Variables

Audio

A variable is a named container that stores a value you can reference later in your program.

In Python, you create one by writing the name, an equals sign, then the value you want to store.

The value can change over time - reassigning the name simply points it to a new value.

1xSarah

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Certificate of Completion

This certifies thatJohn Doehas successfully completed

Python Fundamentals

DateJan 2026

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Why follow this Java roadmap on Coddy

Aimed at the jobs Java actually fills. Java runs enterprise backends, banking and insurance systems, and services at large companies, much of it on Spring; Android apps were written in Java for a decade before Google made Kotlin its preferred language. Every one of those jobs assumes the foundation on this page.
Java past the syntax. The course reaches the parts enterprise code is made of: interfaces and abstract classes, generics with bounds and wildcards, equals() and hashCode(), checked exceptions and try-with-resources, records, and the classic design patterns, ending in a library management project.
Interview practice in Java. The stack, queue, linked list, binary tree and hash table, the recursion challenges and the five sorts are all written in Java, the language many large companies interview in.
Graded, with hints instead of answers. Each lesson closes on a Java challenge that test cases grade; a failing test brings in Bugsy, the AI tutor, who points at the problem in your code without writing the fix. Most courses end with a free certificate, and it all runs in the browser: no JDK, no IDE, no setup.

Frequently asked questions about becoming a Java developer

How long does it take to become a Java developer?

Six to twelve months at about an hour a day is a realistic range from zero to a junior Java interview. On this roadmap the Java course takes six to eight weeks, and its object-oriented section is the part worth doing slowly; the command line, Git and SQL add about a month; the data structures and sorting steps two more. Spring Boot usually comes next, and a small service you built yourself is the strongest thing a junior Java application can show.

Is Java a good first language for a software engineer?

Yes, if you accept a slower first month. Java makes you declare types, wrap code in classes and handle exceptions from the start, which feels heavy on day one and pays off later, because large codebases depend on exactly that discipline. If you have no target yet, Python gets you productive faster, and the software engineer roadmap exists in Python too; if your goal is enterprise backend work, starting in Java means learning your working language only once.

What does a Java developer need to know besides Java?

The command line, Git and SQL, which this roadmap covers, and then the ecosystem around the language: a build tool (Maven or Gradle), Spring Boot for web services, JUnit for tests, and enough about the JVM to read a stack trace, a thread dump or a garbage collection log when a service misbehaves. Of those, Spring is the one Java backend listings ask for by name, so learn it first.

When should a Java developer learn Spring Boot?

After the Java course and the SQL step, not before. Spring Boot hides a lot of machinery behind annotations, and when the Java underneath is shaky its errors read as noise: a missing bean, a proxy that did not apply, a query you did not write. Once interfaces, generics and exceptions feel ordinary and you can read a join, Spring is a few weeks of building rather than a wall.

Which course on this roadmap is not taught in Java?

One: clean code is taught in Python only so far, so it is listed after the steps rather than in step seven. Its principles carry over unchanged, and Robert C. Martin's Clean Code, the book that made many of them famous, has its examples in Java. Every step, the object-oriented project and the coding problems included, is in Java.

Is this Java roadmap free?

Yes. Every course on it is free: the lessons, the Java editor and the Linux terminal in your browser, the test-graded challenges, Bugsy's hints and the certificates. Pro removes the daily energy limit and adds unlimited AI help, and nothing on this roadmap requires it.