When implementing algorithms that process collections or use conditional logic, always verify the exact semantics of operations across different data structures. For conditional operators like the Elvis operator (`?:`), be aware they may follow specific evaluation rules rather than intuitive reference semantics. For example, in SpEL, the Elvis operator checks for values that are non-null AND non-empty for Strings, which is more specific than general truthy/falsy rules from other languages: ```java // This will inject 25 if pop3.port is null OR an empty string @Value("${pop3.port ?: 25}") private int port; ``` For operations that process collections, verify which data structures are actually supported. Selection operations in SpEL work not just on lists and maps, but also on arrays and anything implementing `java.lang.Iterable` or `java.util.Map` interfaces: ```java // Works on lists, arrays, and any Iterable implementation inventors.?[nationality == 'Serbian'] ``` Understanding these semantics ensures your algorithms behave as expected across different data structures and prevents subtle bugs.