Selected standard rules from PMD out of box rule sets. Please refer to the origin rule set file, rule name and version info for future update. Detect when Assert#fail is called improperly. 3 [Origin rule set file rulesets/java/basic.xml] Avoid instantiating Boolean objects; you can reference Boolean.TRUE, Boolean.FALSE, or call Boolean.valueOf() instead. 2 [Origin rule set file rulesets/java/basic.xml] Override both public boolean Object.equals(Object other), and public int Object.hashCode(), or override neither. Even if you are inheriting a hashCode() from a parent class, consider implementing hashCode and explicitly delegating to your superclass. 3 [Origin rule set file rulesets/java/unnecessary.xml] Avoid the use of unnecessary return statements. 3 [Origin rule set file rulesets/java/unnecessary.xml] 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. 3 [Origin rule set file rulesets/java/unusedcode.xml] Detects when a local variable is declared and/or assigned, but not used. 3