Java Coding Problems

179. Debugging lambdas

There are at least three solutions when it comes to debugging lambdas:

• Inspect a stack trace
• Logging
• Rely on IDE support (for example, NetBeans, Eclipse, and IntelliJ IDEA support debugging lambdas out of the box or provide plugins for it)

Let's focus on the first two since relying on an IDE is a very large and specific topic that isn't in the scope of this book.

Inspecting the stack trace of a failure that happened inside a lambda or a stream pipeline can be pretty puzzling. Let's consider the following snippet of code:

List<String> names = Arrays.asList("anna", "bob", null, "mary");names.stream()  .map(s -> s.toUpperCase())  .collect(Collectors.toList());

Since the third element from this list is null, we will get ...