Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

OverrideBothEqualsAndHashcode

Since: PMD 0.4

Priority: Medium

Categories: Style

Remediation Points: 50000

Override both public boolean Object.equals(Object other), and public int Object.hashCode(), or override neither. Even if you are inheriting a hashCode() from a parent class, consider implementing hashCode and explicitly delegating to your superclass.

Example:

public class Bar { // poor, missing a hashcode() method
 public boolean equals(Object o) {
 // do some comparison
 }
}

public class Baz { // poor, missing an equals() method
 public int hashCode() {
 // return some hash value
 }
}

public class Foo { // perfect, both methods provided
 public boolean equals(Object other) {
 // do some comparison
 }
 public int hashCode() {
 // return some hash value
 }
}