Cognitive complexity is the mental difficulty of investigating code as each deeper instruction opens another reasoning path and investigative plan. section 2.1
Code investigation moves both through a method and into the methods it calls. Each jump leaves a plan behind, making the behavior harder to assemble mentally. section 2.1
Manage investigation complexity by asking focused questions:
- Check whether a constructor only creates an object or also changes input-related state. section 2.1
- Check whether a method returns a value, changes object state, or does both. section 2.1
- Choose whether to skip an instruction for a simpler investigation or inspect it for greater certainty. section 2.1
Tracing a decoder
A Decoder loops through input strings, extracts digits, sums them, and returns the total. Understanding the extractor requires opening another investigation plan. section 2.1
Listing 2.1 An example of a method to debug
public class Decoder {
public Integer decode(List<String> input) {
int total = 0;
for (String s : input) {
var digits = new StringDigitExtractor(s).extractDigits();
total += digits.stream().collect(Collectors.summingInt(i -> i));
}
return total;
}
}
Inspect the Java method whose constructor and extractDigits call create the hidden behavior that must be investigated. section 2.1
