Method interpolate
has a Cognitive Complexity of 9 (exceeds 5 allowed). Consider refactoring. Open
public static String interpolate(String input){
if(input != null) {
Pattern p = Pattern.compile(VARIABLE_INTERPOLATION_PATTERN);
Matcher m = p.matcher(input);
if (m.matches()) {
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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
Return an empty collection instead of null. Open
return null;
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- Exclude checks
Returning null
instead of an actual array or collection forces callers of the method to explicitly test for nullity, making them more
complex and less readable.
Moreover, in many cases, null
is used as a synonym for empty.
Noncompliant Code Example
public static List<Result> getResults() { return null; // Noncompliant } public static Result[] getResults() { return null; // Noncompliant } public static void main(String[] args) { Result[] results = getResults(); if (results != null) { // Nullity test required to prevent NPE for (Result result: results) { /* ... */ } } }
Compliant Solution
public static List<Result> getResults() { return Collections.emptyList(); // Compliant } public static Result[] getResults() { return new Result[0]; } public static void main(String[] args) { for (Result result: getResults()) { /* ... */ } }
See
- CERT, MSC19-C. - For functions that return an array, prefer returning an empty array over a null value
- CERT, MET55-J. - Return an empty array or collection instead of a null value for methods that return an array or collection
Return an empty collection instead of null. Open
return null;
- Read upRead up
- Exclude checks
Returning null
instead of an actual array or collection forces callers of the method to explicitly test for nullity, making them more
complex and less readable.
Moreover, in many cases, null
is used as a synonym for empty.
Noncompliant Code Example
public static List<Result> getResults() { return null; // Noncompliant } public static Result[] getResults() { return null; // Noncompliant } public static void main(String[] args) { Result[] results = getResults(); if (results != null) { // Nullity test required to prevent NPE for (Result result: results) { /* ... */ } } }
Compliant Solution
public static List<Result> getResults() { return Collections.emptyList(); // Compliant } public static Result[] getResults() { return new Result[0]; } public static void main(String[] args) { for (Result result: getResults()) { /* ... */ } }
See
- CERT, MSC19-C. - For functions that return an array, prefer returning an empty array over a null value
- CERT, MET55-J. - Return an empty array or collection instead of a null value for methods that return an array or collection
Define and throw a dedicated exception instead of using a generic one. Open
throw new RuntimeException("This exception should not have happened, theres a bug in Resources.path(String, boolean)");
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Using such generic exceptions as Error
, RuntimeException
, Throwable
, and Exception
prevents
calling methods from handling true, system-generated exceptions differently than application-generated errors.
Noncompliant Code Example
public void foo(String bar) throws Throwable { // Noncompliant throw new RuntimeException("My Message"); // Noncompliant }
Compliant Solution
public void foo(String bar) { throw new MyOwnRuntimeException("My Message"); }
Exceptions
Generic exceptions in the signatures of overriding methods are ignored, because overriding method has to follow signature of the throw declaration in the superclass. The issue will be raised on superclass declaration of the method (or won't be raised at all if superclass is not part of the analysis).
@Override public void myMethod() throws Exception {...}
Generic exceptions are also ignored in the signatures of methods that make calls to methods that throw generic exceptions.
public void myOtherMethod throws Exception { doTheThing(); // this method throws Exception }
See
- MITRE, CWE-397 - Declaration of Throws for Generic Exception
- CERT, ERR07-J. - Do not throw RuntimeException, Exception, or Throwable
Add a private constructor to hide the implicit public one. Open
public class Resources {
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Utility classes, which are collections of static
members, are not meant to be instantiated. Even abstract utility classes, which can
be extended, should not have public constructors.
Java adds an implicit public constructor to every class which does not define at least one explicitly. Hence, at least one non-public constructor should be defined.
Noncompliant Code Example
class StringUtils { // Noncompliant public static String concatenate(String s1, String s2) { return s1 + s2; } }
Compliant Solution
class StringUtils { // Compliant private StringUtils() { throw new IllegalStateException("Utility class"); } public static String concatenate(String s1, String s2) { return s1 + s2; } }
Exceptions
When class contains public static void main(String[] args)
method it is not considered as utility class and will be ignored by this
rule.