If an abstract class does not provide any methods, it may be acting as a simple data container that is not meant to be instantiated. In this case, it is probably better to use a private or protected constructor in order to prevent instantiation than make the class misleadingly abstract. AbstractClassWithoutAnyMethod (Priority: 1, Ruleset: Design) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_design.html#abstractclasswithoutanymethod

If an abstract class does not provide any methods, it may be acting as a simple data container that is not meant to be instantiated. In this case, it is probably better to use a private or protected constructor in order to prevent instantiation than make the class misleadingly abstract. AbstractClassWithoutAnyMethod (Priority: 1, Ruleset: Design) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_design.html#abstractclasswithoutanymethod

For any method that returns an collection (such as an array, Collection or Map), it is better to return an empty one rather than a null reference. This removes the need for null checking all results and avoids inadvertent NullPointerExceptions. See Effective Java, 3rd Edition, Item 54: Return empty collections or arrays instead of null ReturnEmptyCollectionRatherThanNull (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_errorprone.html#returnemptycollectionratherthannull

For any method that returns an collection (such as an array, Collection or Map), it is better to return an empty one rather than a null reference. This removes the need for null checking all results and avoids inadvertent NullPointerExceptions. See Effective Java, 3rd Edition, Item 54: Return empty collections or arrays instead of null ReturnEmptyCollectionRatherThanNull (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_errorprone.html#returnemptycollectionratherthannull

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: pmd/pmd-github-action@v1, github/codeql-action/upload-sarif@v2. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

CodeQL Action v2 will be deprecated on December 5th, 2024. Please update all occurrences of the CodeQL Action in your workflow files to v3. For more information, see https://github.blog/changelog/2024-01-12-code-scanning-deprecation-of-codeql-action-v2/

Detects when a class, interface, enum or annotation does not have a package definition. NoPackage (Priority: 3, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_codestyle.html#nopackage

Detects when a class, interface, enum or annotation does not have a package definition. NoPackage (Priority: 3, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_codestyle.html#nopackage

Reports control statements whose body is empty, as well as empty initializers. The checked code constructs are the following: - bodies of `try` statements - `finally` clauses of `try` statements - `switch` statements - `synchronized` statements - `if` statements - loop statements: `while`, `for`, `do .. while` - initializers - blocks used as statements (for scoping) This rule replaces the rules EmptyFinallyBlock, EmptyIfStmt, EmptyInitializer, EmptyStatementBlock, EmptySwitchStatements, EmptySynchronizedBlock, EmptyTryBlock, and EmptyWhileStmt. Notice that {% rule java/errorprone/EmptyCatchBlock %} is still an independent rule. EmptyStatementNotInLoop is replaced by {% rule java/codestyle/UnnecessarySemicolon %}. EmptyControlStatement (Priority: 3, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_codestyle.html#emptycontrolstatement

Catching Throwable errors is not recommended since its scope is very broad. It includes runtime issues such as OutOfMemoryError that should be exposed and managed separately. AvoidCatchingThrowable (Priority: 3, Ruleset: Error Prone) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_errorprone.html#avoidcatchingthrowable

Avoid returning from a finally block, this can discard exceptions. ReturnFromFinallyBlock (Priority: 3, Ruleset: Error Prone) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_errorprone.html#returnfromfinallyblock

Do not use "if" statements whose conditionals are always true or always false. UnconditionalIfStatement (Priority: 3, Ruleset: Error Prone) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_errorprone.html#unconditionalifstatement

Reports control statements whose body is empty, as well as empty initializers. The checked code constructs are the following: - bodies of `try` statements - `finally` clauses of `try` statements - `switch` statements - `synchronized` statements - `if` statements - loop statements: `while`, `for`, `do .. while` - initializers - blocks used as statements (for scoping) This rule replaces the rules EmptyFinallyBlock, EmptyIfStmt, EmptyInitializer, EmptyStatementBlock, EmptySwitchStatements, EmptySynchronizedBlock, EmptyTryBlock, and EmptyWhileStmt. Notice that {% rule java/errorprone/EmptyCatchBlock %} is still an independent rule. EmptyStatementNotInLoop is replaced by {% rule java/codestyle/UnnecessarySemicolon %}. EmptyControlStatement (Priority: 3, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_codestyle.html#emptycontrolstatement

Reports control statements whose body is empty, as well as empty initializers. The checked code constructs are the following: - bodies of `try` statements - `finally` clauses of `try` statements - `switch` statements - `synchronized` statements - `if` statements - loop statements: `while`, `for`, `do .. while` - initializers - blocks used as statements (for scoping) This rule replaces the rules EmptyFinallyBlock, EmptyIfStmt, EmptyInitializer, EmptyStatementBlock, EmptySwitchStatements, EmptySynchronizedBlock, EmptyTryBlock, and EmptyWhileStmt. Notice that {% rule java/errorprone/EmptyCatchBlock %} is still an independent rule. EmptyStatementNotInLoop is replaced by {% rule java/codestyle/UnnecessarySemicolon %}. EmptyControlStatement (Priority: 3, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_codestyle.html#emptycontrolstatement

The isEmpty() method on java.util.Collection is provided to determine if a collection has any elements. Comparing the value of size() to 0 does not convey intent as well as the isEmpty() method. UseCollectionIsEmpty (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.0.0-rc4/pmd_rules_java_bestpractices.html#usecollectionisempty