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

Position literals first in all String comparisons, if the second argument is null then NullPointerExceptions can be avoided, they will just return false. Note that switching literal positions for compareTo and compareToIgnoreCase may change the result, see examples. Note that compile-time constant strings are treated like literals. This is because they are inlined into the class file, are necessarily non-null, and therefore cannot cause an NPE at runtime. LiteralsFirstInComparisons (Priority: 1, Ruleset: Best Practices) https://docs.pmd-code.org/snapshot/pmd_rules_java_bestpractices.html#literalsfirstincomparisons

Position literals first in all String comparisons, if the second argument is null then NullPointerExceptions can be avoided, they will just return false. Note that switching literal positions for compareTo and compareToIgnoreCase may change the result, see examples. Note that compile-time constant strings are treated like literals. This is because they are inlined into the class file, are necessarily non-null, and therefore cannot cause an NPE at runtime. LiteralsFirstInComparisons (Priority: 1, Ruleset: Best Practices) https://docs.pmd-code.org/snapshot/pmd_rules_java_bestpractices.html#literalsfirstincomparisons

Position literals first in all String comparisons, if the second argument is null then NullPointerExceptions can be avoided, they will just return false. Note that switching literal positions for compareTo and compareToIgnoreCase may change the result, see examples. Note that compile-time constant strings are treated like literals. This is because they are inlined into the class file, are necessarily non-null, and therefore cannot cause an NPE at runtime. LiteralsFirstInComparisons (Priority: 1, Ruleset: Best Practices) https://docs.pmd-code.org/snapshot/pmd_rules_java_bestpractices.html#literalsfirstincomparisons

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

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: 1, Ruleset: Best Practices) https://docs.pmd-code.org/snapshot/pmd_rules_java_bestpractices.html#unusedlocalvariable

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

Uncommented Empty Constructor finds instances where a constructor does not contain statements, but there is no comment. By explicitly commenting empty constructors it is easier to distinguish between intentional (commented) and unintentional empty constructors. UncommentedEmptyConstructor (Priority: 1, Ruleset: Documentation) https://docs.pmd-code.org/snapshot/pmd_rules_java_documentation.html#uncommentedemptyconstructor

In some cases, explicit type arguments in a constructor call for a generic type may be replaced by diamond type arguments (`<>`), and be inferred by the compiler. This rule recommends that you use diamond type arguments anywhere possible, since it avoids duplication of the type arguments, and makes the code more concise and readable. This rule is useful when upgrading a codebase to Java 1.7, Java 1.8, or Java 9. The diamond syntax was first introduced in Java 1.7. In Java 8, improvements in Java's type inference made more type arguments redundant. In Java 9, type arguments inference was made possible for anonymous class constructors. UseDiamondOperator (Priority: 1, Ruleset: Code Style) https://docs.pmd-code.org/snapshot/pmd_rules_java_codestyle.html#usediamondoperator

Excessive coupling to implementation types (e.g., `HashSet`) limits your ability to use alternate implementations in the future as requirements change. Whenever available, declare variables and parameters using a more general type (e.g, `Set`). This rule reports uses of concrete collection types. User-defined types that should be treated the same as interfaces can be configured with the property `allowedTypes`. LooseCoupling (Priority: 1, Ruleset: Best Practices) https://docs.pmd-code.org/snapshot/pmd_rules_java_bestpractices.html#loosecoupling