Functional Programming in Java

Cleaning Up Resources

GC can be a pain to deal with. A company asked me to help debug a problem—one programmer described the issue as “it works fine…most of the time.” The application failed during peak usage. It turned out that the code was relying on the finalize method to release database connections. The JVM figured it had enough memory and opted not to run GC. Since the finalizer was rarely invoked, it led to external resource clogging and the resulting failure.

We need to manage situations like this in a better way, and lambda expressions can help. Let’s start with an example problem that involves GC. We’ll build the example using a few different approaches, discussing the merits and deficiencies of each. This will help us see the strengths ...