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

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

Checks that each top-level class, interface, enumor annotation resides in a source file of its own.Official description of a 'top-level' term:7.6. Top Level Type Declarations.If file doesn't contains public class, interface, enum or annotation,top-level type is the first type in file.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or staticmembers from a class leads to tight coupling between packagesor classes and might lead to problems when a new version of alibrary introduces name clashes.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that each top-level class, interface, enumor annotation resides in a source file of its own.Official description of a 'top-level' term:7.6. Top Level Type Declarations.If file doesn't contains public class, interface, enum or annotation,top-level type is the first type in file.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or staticmembers from a class leads to tight coupling between packagesor classes and might lead to problems when a new version of alibrary introduces name clashes.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Validates abbreviations (consecutive capital letters) length in identifier name,it also allows to enforce camel case naming. Please read more atGoogle Style Guideto get to know how to avoid long abbreviations in names.

allowedAbbreviationLength specifies how many consecutive capital letters areallowed in the identifier.A value of 3 indicates that up to 4 consecutive capital letters are allowed,one after the other, before a violation is printed. The identifier 'MyTEST' would beallowed, but 'MyTESTS' would not be.A value of 0 indicates that only 1 consecutive capital letter is allowed. Thisis what should be used to enforce strict camel casing. The identifier 'MyTest' wouldbe allowed, but 'MyTEst' would not be.

ignoreFinal, ignoreStatic, and ignoreStaticFinalcontrol whether variables with the respective modifiers are to be ignored.Note that a variable that is both static and final will always be considered underignoreStaticFinal only, regardless of the values of ignoreFinaland ignoreStatic. So for example if ignoreStatic is true butignoreStaticFinal is false, then static final variables will not be ignored.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that each variable declaration is in its own statement and onits own line.

Rationale: the Java code conventions chapter 6.1 recommends thatdeclarations should be one per line/statement.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or staticmembers from a class leads to tight coupling between packagesor classes and might lead to problems when a new version of alibrary introduces name clashes.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that local, non-final variable names conform to a specified pattern.A catch parameter is considered to be a local variable.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or staticmembers from a class leads to tight coupling between packagesor classes and might lead to problems when a new version of alibrary introduces name clashes.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or staticmembers from a class leads to tight coupling between packagesor classes and might lead to problems when a new version of alibrary introduces name clashes.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that method parameter names conform to a specified pattern.By using accessModifiers property it is possibleto specify different formats for methods at different visibility levels.

To validate catch parameters please useCatchParameterName.

To validate lambda parameters please useLambdaParameterName.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that local, non-final variable names conform to a specified pattern.A catch parameter is considered to be a local variable.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for empty line separators before package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

Checks for empty line separators before not only statements butimplementation and documentation comments and blocks as well.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for braces around code blocks.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.