lots of exercises in java... from https://github.com/exercism/java

Stuart Kent 54cf4a6c28 Restructure exercise directory Reference solution directory was renamed and move to the always-excluded-from-delivery .meta folder.		9 vuotta sitten
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.meta/src/reference/java	Restructure exercise directory	9 vuotta sitten
src	Restructure exercise directory	9 vuotta sitten
README.md	Replace exercise templates with track-level default	9 vuotta sitten
build.gradle	complex-numbers: add to track	9 vuotta sitten

Complex Numbers

A complex number is a number in the form a + b * i where a and b are real and i satisfies i^2 = -1.

Assume the programming language you are using does not have an implementation of complex numbers.

To run the tests:

$ gradle test

For more detailed info about the Java track see the help page.

Source

It's possible to submit an incomplete solution so you can see how others have completed the exercise.