These are just a collection of samples I wrote down while preparing my Java courses here and there.

Most of the examples works fine with any Java version from 5 on. Some of them are specific for Java 7 and Java 8.

• Modern Java development: https://github.com/giorgiosironi/game-of-life-modern-java
• Awesome Java: https://github.com/akullpp/awesome-java
• Awesome Java8: https://github.com/tedyoung/awesome-java8
• A list of useful Java frameworks, libraries, software and hello worlds examples: https://github.com/Vedenin/useful-java-links

• Java Koans: https://github.com/matyb/java-koans
• Programmr | Your Online Code Lab: http://www.programmr.com/challenges/palindrom-string-2
• Coder Dojo: http://cyber-dojo.org/setup/show_exercises/?language=Java&test=JUnit
• CodingBat, code practice (http://codingbat.com/java)

• String Calculator (https://github.com/xpeppers/string-calculator-kata)
• Bowling Game Kata (http://butunclebob.com/ArticleS.UncleBob.TheBowlingGameKata)
• Sales Tax Kata (https://github.com/xpeppers/sales-taxes-problem)
• Number Gaps Kata (https://github.com/andreabertagnolli/numbers-gaps-kata)
• Opening Hours Kata (https://github.com/christian-fei/opening-hours-kata)

• GildedRose Refactoring Kata: https://github.com/emilybache/GildedRose-Refactoring-Kata
• Tennis Refactoring Kata: https://github.com/emilybache/Tennis-Refactoring-Kata

• Racing Car Katas: https://github.com/emilybache/Racing-Car-Katas

• "Clean Code” by Robert C. Martin (http://www.amazon.it/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882), really a great starter book.

  • See also UncleBob's videos at https://cleancoders.com

• "Effective Java" by J.Bloch, to learn the idiomatic way to Java :)