Reports classes that may be made final because they cannot be extended from outside their compilation unit anyway. This is because all their constructors are private, so a subclass could not call the super constructor. ClassWithOnlyPrivateConstructorsShouldBeFinal (Priority: 1, Ruleset: Design) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_design.html#classwithonlyprivateconstructorsshouldbefinal

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Switch statements should be exhaustive, to make their control flow easier to follow. This can be achieved by adding a `default` case, or, if the switch is on an enum type, by ensuring there is one switch branch for each enum constant. This rule doesn't consider Switch Statements, that use Pattern Matching, since for these the compiler already ensures that all cases are covered. The same is true for Switch Expressions, which are also not considered by this rule. NonExhaustiveSwitch (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#nonexhaustiveswitch

Detects when a local variable is declared and/or assigned, but not used. Variables whose name starts with `ignored` or `unused` are filtered out. UnusedLocalVariable (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#unusedlocalvariable

Detects when a local variable is declared and/or assigned, but not used. Variables whose name starts with `ignored` or `unused` are filtered out. UnusedLocalVariable (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#unusedlocalvariable

Detects when a local variable is declared and/or assigned, but not used. Variables whose name starts with `ignored` or `unused` are filtered out. UnusedLocalVariable (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#unusedlocalvariable

Detects when a local variable is declared and/or assigned, but not used. Variables whose name starts with `ignored` or `unused` are filtered out. UnusedLocalVariable (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#unusedlocalvariable

Detects when a private field is declared and/or assigned a value, but not used. Since PMD 6.50.0 private fields are ignored, if the fields are annotated with any annotation or the enclosing class has any annotation. Annotations often enable a framework (such as dependency injection, mocking or e.g. Lombok) which use the fields by reflection or other means. This usage can't be detected by static code analysis. Previously these frameworks where explicitly allowed by listing their annotations in the property "ignoredAnnotations", but that turned out to be prone of false positive for any not explicitly considered framework. UnusedPrivateField (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#unusedprivatefield

Java allows the use of several variables declaration of the same type on one line. However, it can lead to quite messy code. This rule looks for several declarations on the same line. OneDeclarationPerLine (Priority: 4, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#onedeclarationperline

Java allows the use of several variables declaration of the same type on one line. However, it can lead to quite messy code. This rule looks for several declarations on the same line. OneDeclarationPerLine (Priority: 4, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_bestpractices.html#onedeclarationperline

Reports fields which may be converted to a local variable. This is so because in every method where the field is used, it is assigned before it is first read. Hence, the value that the field had before the method call may not be observed, so it might as well not be stored in the enclosing object. Limitations: * We can only check private fields for now. * The rule is not aware of threading, so it may cause false positives in concurrent code. Such FPs are best handled by suppression (see also the `ignoredAnnotations` property). SingularField (Priority: 3, Ruleset: Design) https://docs.pmd-code.org/pmd-doc-7.8.0/pmd_rules_java_design.html#singularfield