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: 1, Ruleset: Code Style) https://docs.pmd-code.org/snapshot/pmd_rules_java_codestyle.html#uselessparentheses

Ensure that resources (like `java.sql.Connection`, `java.sql.Statement`, and `java.sql.ResultSet` objects and any subtype of `java.lang.AutoCloseable`) are always closed after use. Failing to do so might result in resource leaks. Note: It suffices to configure the super type, e.g. `java.lang.AutoCloseable`, so that this rule automatically triggers on any subtype (e.g. `java.io.FileInputStream`). Additionally specifying `java.sql.Connection` helps in detecting the types, if the type resolution / auxclasspath is not correctly setup. Note: Since PMD 6.16.0 the default value for the property `types` contains `java.lang.AutoCloseable` and detects now cases where the standard `java.io.*Stream` classes are involved. In order to restore the old behaviour, just remove "AutoCloseable" from the types. CloseResource (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#closeresource

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: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#avoidcatchingthrowable

Ensure that resources (like `java.sql.Connection`, `java.sql.Statement`, and `java.sql.ResultSet` objects and any subtype of `java.lang.AutoCloseable`) are always closed after use. Failing to do so might result in resource leaks. Note: It suffices to configure the super type, e.g. `java.lang.AutoCloseable`, so that this rule automatically triggers on any subtype (e.g. `java.io.FileInputStream`). Additionally specifying `java.sql.Connection` helps in detecting the types, if the type resolution / auxclasspath is not correctly setup. Note: Since PMD 6.16.0 the default value for the property `types` contains `java.lang.AutoCloseable` and detects now cases where the standard `java.io.*Stream` classes are involved. In order to restore the old behaviour, just remove "AutoCloseable" from the types. CloseResource (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#closeresource

Empty Catch Block finds instances where an exception is caught, but nothing is done. In most circumstances, this swallows an exception which should either be acted on or reported. EmptyCatchBlock (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#emptycatchblock

Empty Catch Block finds instances where an exception is caught, but nothing is done. In most circumstances, this swallows an exception which should either be acted on or reported. EmptyCatchBlock (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#emptycatchblock

Empty Catch Block finds instances where an exception is caught, but nothing is done. In most circumstances, this swallows an exception which should either be acted on or reported. EmptyCatchBlock (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#emptycatchblock

Empty Catch Block finds instances where an exception is caught, but nothing is done. In most circumstances, this swallows an exception which should either be acted on or reported. EmptyCatchBlock (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#emptycatchblock

Empty Catch Block finds instances where an exception is caught, but nothing is done. In most circumstances, this swallows an exception which should either be acted on or reported. EmptyCatchBlock (Priority: 1, Ruleset: Error Prone) https://docs.pmd-code.org/snapshot/pmd_rules_java_errorprone.html#emptycatchblock