Add book "Java by Comparison" (#68)

readme.md

@@ -820,6 +820,8 @@ _Please read [contribution guidelines](contributing.md) before contributing._
 - [📕 Java 8 in action (2014)](https://www.goodreads.com/book/show/20534354-java-8-in-action)
 - [📕 Test-driven Java development (2015)](https://www.goodreads.com/book/show/26333479-test-driven-java-development)
 - [📕 Java SE 11 Programmer I Certification Guide (2020 early-access)](https://www.manning.com/books/java-se-11-programmer-i-certification-guide)
+- [📕 Java by Comparison (2018)](https://www.goodreads.com/book/show/39339133-java-by-comparison)
+  - [Code examples](https://github.com/javabycomparison/samplecode)
 
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