Add new Java exercises

One of the easiest ways to add new exercises to the Java track is to translate them from other language tracks on Exercism. This page lists all of the problem specifications in the common pool of exercises which have not yet been implemented in Java.

The icon links to the language-independent description of the problem.

The icon links to the canonical test data.

We also link to all the implementations of each exercise in other languages, which you can use for inspiration.

Once you've picked an exercise, follow the instructions in this guide and submit your pull request to the Java track repository on GitHub.





Implement a basic reactive system.


Compute the result for a game of Hex / Polygon


Write a function to solve alphametics puzzles.


Make a chain of dominoes.

Parallel Letter Frequency

Count the frequency of letters in texts using parallel computation.


Creating a zipper for a binary tree.

Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

Variable Length Quantity

Implement variable length quantity encoding and decoding.

Diffie Hellman

Diffie-Hellman key exchange.


Reparent a graph on a selected node


For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.

Two Bucket

Given two buckets of different size, demonstrate how to measure an exact number of liters.


Refactor a Markdown parser

Zebra Puzzle

Solve the zebra puzzle.

Error Handling

Implement various kinds of error handling and resource management


Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.

Scale Generator

Generate musical scales, given a starting note and a set of intervals.

Go Counting

Count the scored points on a Go board.

Sgf Parsing

Parsing a Smart Game Format string.

Tree Building

Refactor a tree building algorithm.

Dot Dsl

Write a Domain Specific Language similar to the Graphviz dot language


Implement the logic of the hangman game using functional reactive programming.


Refactor a ledger printer.

Lens Person

Use lenses to update nested records (specific to languages with immutable data).

Reverse String

Reverse a string


Report network IO statistics