Merge pull request #5153 from mP1/feature/SpreadsheetComparatorNameLi…

…st-empty SpreadsheetComparatorNameList.EMPTY
mP1 · Sep 21, 2024 · ddc4887 · ddc4887
2 parents b32445f + ac82ec8
commit ddc4887
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Showing 2 changed files with 35 additions and 1 deletion.
diff --git a/src/main/java/walkingkooka/spreadsheet/compare/SpreadsheetComparatorNameList.java b/src/main/java/walkingkooka/spreadsheet/compare/SpreadsheetComparatorNameList.java
@@ -38,6 +38,13 @@ public final class SpreadsheetComparatorNameList extends AbstractList<Spreadshee
         implements ImmutableListDefaults<SpreadsheetComparatorNameList, SpreadsheetComparatorName>,
         HasText {
 
+    /**
+     * An empty {@link SpreadsheetComparatorNameList}.
+     */
+    public final static SpreadsheetComparatorNameList EMPTY = SpreadsheetComparatorNameList.with(
+            Lists.empty()
+    );
+
     /**
      * Parses a CSV string of {@link SpreadsheetComparatorName names} into a {@link SpreadsheetComparatorNameList}.
      */
@@ -57,11 +64,26 @@ public static SpreadsheetComparatorNameList with(final List<SpreadsheetComparato
 
         return names instanceof SpreadsheetComparatorNameList ?
                 (SpreadsheetComparatorNameList) names :
-                new SpreadsheetComparatorNameList(
+                with0(
                         Lists.immutable(names)
                 );
     }
 
+    private static SpreadsheetComparatorNameList with0(final List<SpreadsheetComparatorName> names) {
+        final SpreadsheetComparatorNameList list;
+
+        switch(names.size()) {
+            case 0:
+              list = EMPTY;
+              break;
+            default:
+                list = new SpreadsheetComparatorNameList(names);
+                break;
+        }
+
+        return list;
+    }
+
     private SpreadsheetComparatorNameList(final List<SpreadsheetComparatorName> names) {
         this.names = names;
     }

diff --git a/src/test/java/walkingkooka/spreadsheet/compare/SpreadsheetComparatorNameListTest.java b/src/test/java/walkingkooka/spreadsheet/compare/SpreadsheetComparatorNameListTest.java
@@ -56,6 +56,18 @@ public void testWithDoesntDoubleWrap() {
         );
     }
 
+    @Test
+    public void testWithEmpty() {
+        assertSame(
+                SpreadsheetComparatorNameList.EMPTY,
+                SpreadsheetComparatorNameList.with(
+                        Lists.empty()
+                )
+        );
+    }
+
+    // list.............................................................................................................
+
     @Test
     public void testGet() {
         this.getAndCheck(