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

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