Mockito Made Clear
Pragmatic Bookshelf, January 2023. Stubs, mocks, and spies — and why the framework does what it does.
Modern Java Recipes
O'Reilly Media, September 2017. More than 70 recipes covering Java SE 8's functional features (with a look ahead at Java 9).
Making Java Groovy
Manning, September 2013. Blending Groovy into day-to-day work with Java.