Add a private constructor to hide the implicit public one. Open
final class Utility {
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- Exclude checks
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.
Define and throw a dedicated exception instead of using a generic one. Open
throw new RuntimeException(e);
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- Exclude checks
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
Identical blocks of code found in 2 locations. Consider refactoring. Open
private static Diagrams compile(InputStream stream) {
Diagrams diagrams = new Diagrams();
Input input = parse(stream);
for (Grammar grammar : input.grammars()) {
Diagram diagram = grammar.diagram(input.importMap());
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Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 66.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76