Fix SAT warnings (#14202)

* Fix SAT warnings

- checkstyle.ModifierOrderCheck
- checkstyle.OneStatementPerLineCheck
- checkstyle.NeedBracesCheck
- PMD.UseStandardCharsets
- PMD.UseCollectionIsEmpty
- PMD.UnusedLocalVariable
- PMD.SimplifyBooleanReturns where reasonable, suppress where
readability is better without change
- PMD.SimplifyBooleanExpressions

* Include StandardCharsets

Signed-off-by: Holger Friedrich <mail@holger-friedrich.de>

bundles/org.openhab.binding.luxom/src/main/java/org/openhab/binding/luxom/internal/handler/util/PercentageConverter.java

@@ -30,8 +30,9 @@ public class PercentageConverter {
      * @return if hexRepresentation == null return -1, otherwise return percentage
      */
     public static int getPercentage(@Nullable String hexRepresentation) {
-        if (hexRepresentation == null)
+        if (hexRepresentation == null) {
             return -1;
+        }
         int decimal = Integer.parseInt(hexRepresentation, 16);
         BigDecimal level = new BigDecimal(100 * decimal).divide(new BigDecimal(255), RoundingMode.FLOOR);
         return level.intValue();