Java Functional Programming

Java 8 introduces lambda expression, allowing non-verbose, no-memory-leak functional programming.

Guava documentation warns you about the verboseness of using anonymous classes to approximate functional programming. Anonymous classes are also often guilty of unnecessary object retention (memory leak) because they always hold a strong reference to their enclosing instance.

Java 8 lambda expression is unlikely to suffer from these problems (quote: “while inner class instances always hold a strong reference to their enclosing instance, lambdas that do not capture members from the enclosing instance do not hold a reference to it.”).

Additionally, lambda expression consumes less memory than anonymous class because it is implemented with invokedynamic introduced since Java 7. And lambda expression is comparable in performance to anonymous class (but JVM seems to need longer time to warm up lambda expression?).

Here is a good explanation of lambda under the hood.