Functional Programming in Java

Foreword

Venkat Subramaniam would never be described as a “waterfall” sort of guy. So, when he mentioned that he was starting on a Java 8 book—long before the design of Java 8 was settled—I was not at all surprised. It was clear this was going to be an “agile” book project.

Despite having to more than occasionally rework the text as the language and library features evolved, Venkat had a secret advantage—he knew where we were going. The Java 8 design was heavily influenced by the core principles of functional programming: functions as values, immutability, and statelessness. We didn’t do this because functional programming is trendy or cool; we did it because programs that are expressed as stateless transformations on immutable data, rather than ...