Minor code simplifications and improvements

src/main/java/ch/poole/openinghoursparser/TimeSpan.java

@@ -70,9 +70,7 @@ public String toString() {
         if (startEvent != null) {
             b.append(startEvent.toString());
         } else {
-            b.append(String.format(Locale.US, "%02d", start / 60));
-            b.append(":");
-            b.append(String.format(Locale.US, "%02d", start % 60));
+            appendTime(b, start);
         }
         if (endEvent != null) {
             b.append("-");
@@ -81,22 +79,31 @@ public String toString() {
             b.append("-");
             // output as normal time if time span is less than 24 hours
             int tempEnd = start != UNDEFINED_TIME && (end - start) < HOURS_24 && end > HOURS_24 ? end - HOURS_24 : end;
-            b.append(String.format(Locale.US, "%02d", tempEnd / 60));
-            b.append(":");
-            b.append(String.format(Locale.US, "%02d", end % 60));
+            appendTime(b, tempEnd);
         }
         if (openEnded) {
             b.append("+");
         }
         if (interval != 0) { // output only the full format
             b.append("/");
-            b.append(String.format(Locale.US, "%02d", interval / 60));
-            b.append(":");
-            b.append(String.format(Locale.US, "%02d", interval % 60));
+            appendTime(b, interval);
+
         }
         return b.toString();
     }
 
+    /**
+     * Append a minute value as a time to the StringBuilder
+     * 
+     * @param b the StringBuilder
+     * @param minutes the number of minutes
+     */
+    private void appendTime(@NotNull StringBuilder b, int minutes) {
+        b.append(String.format(Locale.US, "%02d", minutes / 60));
+        b.append(":");
+        b.append(String.format(Locale.US, "%02d", minutes % 60));
+    }
+
     @Override
     public boolean equals(Object other) {
         if (this == other) {
@@ -170,12 +177,22 @@ public int getInterval() {
      * @param s the start value to set
      */
     public void setStart(int s) {
-        if (s != UNDEFINED_TIME && (s < MIN_TIME || s > MAX_EXTENDED_TIME)) {
+        if (invalidTime(s)) {
             throw new IllegalArgumentException(tr("invalid_time", s));
         }
         this.start = s;
     }
 
+    /**
+     * Check if time is valid/invalid
+     * 
+     * @param t the time value
+     * @return true if invalid
+     */
+    private boolean invalidTime(int t) {
+        return t != UNDEFINED_TIME && (t < MIN_TIME || t > MAX_EXTENDED_TIME);
+    }
+
     /**
      * @param startEvent the startEvent to set
      */
@@ -189,7 +206,7 @@ public void setStartEvent(VariableTime startEvent) {
      * @param e the end value to set
      */
     public void setEnd(int e) {
-        if (e != UNDEFINED_TIME && (e < MIN_TIME || e > MAX_EXTENDED_TIME)) {
+        if (invalidTime(e)) {
             throw new IllegalArgumentException(tr("invalid_time", e));
         }
         this.end = e;

src/main/java/ch/poole/openinghoursparser/Util.java

@@ -92,20 +92,21 @@ private static String rulesToOpeningHoursString(@NotNull List<Rule> rules, boole
         StringBuilder result = new StringBuilder();
         boolean first = true;
         for (Rule r : rules) {
-            if (!r.isEmpty()) {
-                if (!first) {
-                    if (r.isAdditive()) {
-                        result.append(", ");
-                    } else if (r.isFallBack()) {
-                        result.append(" || ");
-                    } else {
-                        result.append("; ");
-                    }
+            if (r.isEmpty()) {
+                continue;
+            }
+            if (!first) {
+                if (r.isAdditive()) {
+                    result.append(", ");
+                } else if (r.isFallBack()) {
+                    result.append(" || ");
                 } else {
-                    first = false;
+                    result.append("; ");
                 }
-                result.append(debug ? r.toDebugString() : r.toString());
+            } else {
+                first = false;
             }
+            result.append(debug ? r.toDebugString() : r.toString());
         }
         return result.toString();
     }
@@ -145,19 +146,19 @@ public static String capitalize(String s) {
     public static String deWeekDays2En(String s) {
         switch (s.toLowerCase(Locale.US)) {
         case "mo":
-            return "Mo";
+            return WeekDay.MO.toString();
         case "di":
-            return "Tu";
+            return WeekDay.TU.toString();
         case "mi":
-            return "We";
+            return WeekDay.WE.toString();
         case "do":
-            return "Th";
+            return WeekDay.TH.toString();
         case "fr":
-            return "Fr";
+            return WeekDay.FR.toString();
         case "sa":
-            return "Sa";
+            return WeekDay.SA.toString();
         case "so":
-            return "Su";
+            return WeekDay.SU.toString();
         default:
             return null;
         }
@@ -173,7 +174,7 @@ public static String deWeekDays2En(String s) {
     @SuppressWarnings("unchecked")
     static <T extends Copy<?>> List<T> copyList(List<T> l) {
         if (l == null) {
-            return null;
+            return null; // NOSONAR
         }
         List<T> r = new ArrayList<>(l.size());
         for (T o : l) {
@@ -216,8 +217,8 @@ static boolean between(@NotNull String token, int lower, int upper) {
     }
 
     /**
-     * Returns {@code true} if the arguments are equal to each other
-     * and {@code false} otherwise.
+     * Returns {@code true} if the arguments are equal to each other and {@code false} otherwise.
+     * 
      * @param a the first object
      * @param b the second object
      * @return true if the arguments are equal