2018
https://www.javaworld.com/article/3290403/core-java/java-challengers-3-polymorphism-and-inheritance.html
    https://habr.com/company/otus/blog/429120/
https://www.javaworld.com/article/3276354/java-language/java-challengers-2-string-comparisons.html
    https://habr.com/company/otus/blog/428449/
https://www.javaworld.com/article/3268983/learn-java/java-challengers-1-method-overloading-in-the-jvm.html
    https://habr.com/company/otus/blog/428307/