valid8j (pronounced validate-j) is a DbC (design by contract[1]) library named after valid4j[2]. It uses pcond, which provides you with predicates that can print descriptive message on a failure, instead of hamcrest used by valid4j. The benefit of pcond over hamcrest is its compatibility and extensibility. Instead of "matchers" that hamcrest uses to verify values, pcond uses Java’s plain Predicate and provide useful preset predicates from which you can build your own predicates for complex types. So, you can reuse the predicates you created for assertions for other purposes, such as value checking and testing.

For full documentation, visit here. Also, check its overview.

Have a following maven dependency in your pom.xml.

Visit oss.sonatype.org to figure out the most recent version of valid8j-pcond.

• [1] Wikipedia article on Design by Contract, https://en.wikipedia.org/wiki/Design_by_contract

• [2] Valid4j, http://www.valid4j.org