Fix sort by priority (#6222) (#6265)

* Fix sort by priority (#6222)

* Change in CHANGELOG.

CHANGELOG.md

@@ -27,6 +27,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 
 ### Fixed
 
+- We fixed an issue where sort by priority was broken. [#6222](https://github.com/JabRef/jabref/issues/6222)
 - We fixed an issue where opening a library from the recent libraries menu was not possible. [#5939](https://github.com/JabRef/jabref/issues/5939)
 - We fixed an issue with inconsistent capitalization of file extensions when downloading files [#6115](https://github.com/JabRef/jabref/issues/6115)
 - We fixed the display of language and encoding in the preferences dialog. [#6130](https://github.com/JabRef/jabref/pull/6130)

src/main/java/org/jabref/gui/maintable/MainTableColumnFactory.java

@@ -38,6 +38,7 @@
 import org.jabref.gui.specialfields.SpecialFieldsPreferences;
 import org.jabref.gui.util.OptionalValueTableCellFactory;
 import org.jabref.gui.util.ValueTableCellFactory;
+import org.jabref.gui.util.comparator.PriorityFieldComparator;
 import org.jabref.gui.util.comparator.RankingFieldComparator;
 import org.jabref.gui.util.comparator.ReadStatusFieldComparator;
 import org.jabref.logic.l10n.Localization;
@@ -316,6 +317,10 @@ private TableColumn<BibEntryTableViewModel, Optional<SpecialFieldValueViewModel>
             column.setComparator(new ReadStatusFieldComparator());
         }
 
+        if (specialField == SpecialField.PRIORITY) {
+            column.setComparator(new PriorityFieldComparator());
+        }
+
         column.setSortable(true);
 
         return column;

src/main/java/org/jabref/gui/util/comparator/PriorityFieldComparator.java

@@ -0,0 +1,27 @@
+package org.jabref.gui.util.comparator;
+
+import java.util.Comparator;
+import java.util.Optional;
+
+import org.jabref.gui.specialfields.SpecialFieldValueViewModel;
+
+public class PriorityFieldComparator implements Comparator<Optional<SpecialFieldValueViewModel>> {
+
+    @Override
+    public int compare(Optional<SpecialFieldValueViewModel> val1, Optional<SpecialFieldValueViewModel> val2) {
+        if (val1.isPresent()) {
+            if (val2.isPresent()) {
+                return val1.get().getValue().compareTo(val2.get().getValue());
+            } else {
+                return -1;
+            }
+        } else {
+            if (val2.isPresent()) {
+                return 1;
+            } else {
+                return 0;
+            }
+        }
+    }
+
+}