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-7.6.0/pmd_rules_java_design.html#classwithonlyprivateconstructorsshouldbefinal

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-7.6.0/pmd_rules_java_design.html#classwithonlyprivateconstructorsshouldbefinal

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

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-7.6.0/pmd_rules_java_design.html#classwithonlyprivateconstructorsshouldbefinal

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

Whenever using a log level, one should check if it is actually enabled, or otherwise skip the associate String creation and manipulation, as well as any method calls. An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework. GuardLogStatement (Priority: 2, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#guardlogstatement

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. SwitchStmtsShouldHaveDefault (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#switchstmtsshouldhavedefault

Uncommented Empty Method Body finds instances where a method body does not contain statements, but there is no comment. By explicitly commenting empty method bodies it is easier to distinguish between intentional (commented) and unintentional empty methods. UncommentedEmptyMethodBody (Priority: 3, Ruleset: Documentation) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_documentation.html#uncommentedemptymethodbody

Annotating overridden methods with @OverRide ensures at compile time that the method really overrides one, which helps refactoring and clarifies intent. MissingOverride (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#missingoverride

Parenthesized expressions are used to override the default operator precedence rules. Parentheses whose removal would not change the relative nesting of operators are unnecessary, because they don't change the semantics of the enclosing expression. Some parentheses that strictly speaking are unnecessary, may still be considered useful for readability. This rule allows to ignore violations on two kinds of unnecessary parentheses: - "Clarifying" parentheses, which separate operators of difference precedence. While unnecessary, they make precedence rules explicit, which may be useful for rarely used operators. For example: ```java (a + b) & c // is equivalent to `a + b & c`, but probably clearer ``` Unset the property `ignoreClarifying` to report them. - "Balancing" parentheses, which are unnecessary but visually balance out another pair of parentheses around an equality operator. For example, those two expressions are equivalent: ```java (a == null) != (b == null) a == null != (b == null) ``` The parentheses on the right are required, and the parentheses on the left are just more visually pleasing. Unset the property `ignoreBalancing` to report them. UselessParentheses (Priority: 4, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_codestyle.html#uselessparentheses

An operation on an Immutable object (String, BigDecimal or BigInteger) won't change the object itself since the result of the operation is a new object. Therefore, ignoring the operation result is an error. UselessOperationOnImmutable (Priority: 3, Ruleset: Error Prone) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_errorprone.html#uselessoperationonimmutable

Reports loops that can be safely replaced with the foreach syntax. The rule considers loops over lists, arrays and iterators. A loop is safe to replace if it only uses the index variable to access an element of the list or array, only has one update statement, and loops through *every* element of the list or array left to right. ForLoopCanBeForeach (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#forloopcanbeforeach

Reports loops that can be safely replaced with the foreach syntax. The rule considers loops over lists, arrays and iterators. A loop is safe to replace if it only uses the index variable to access an element of the list or array, only has one update statement, and loops through *every* element of the list or array left to right. ForLoopCanBeForeach (Priority: 3, Ruleset: Best Practices) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_bestpractices.html#forloopcanbeforeach

Non-thread safe singletons can result in bad state changes. Eliminate static singletons if possible by instantiating the object directly. Static singletons are usually not needed as only a single instance exists anyway. Other possible fixes are to synchronize the entire method or to use an [initialize-on-demand holder class](https://en.wikipedia.org/wiki/Initialization-on-demand_holder_idiom). Refrain from using the double-checked locking pattern. The Java Memory Model doesn't guarantee it to work unless the variable is declared as `volatile`, adding an uneeded performance penalty. [Reference](http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html) See Effective Java, item 48. NonThreadSafeSingleton (Priority: 3, Ruleset: Multithreading) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_multithreading.html#nonthreadsafesingleton

Reports qualified this usages in the same class. UselessQualifiedThis (Priority: 3, Ruleset: Code Style) https://docs.pmd-code.org/pmd-doc-7.6.0/pmd_rules_java_codestyle.html#uselessqualifiedthis