toImmutable() method on FastList avoids creating a redundant array copy

Signed-off-by: vmzakharov <zakharov.vladimir.m@gmail.com>
eclipse · May 14, 2020 · 753dae6 · 753dae6
1 parent cc17ca5
commit 753dae6
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/...s/src/main/java/org/eclipse/collections/impl/list/immutable/ImmutableListFactoryImpl.java b/...s/src/main/java/org/eclipse/collections/impl/list/immutable/ImmutableListFactoryImpl.java
@@ -229,7 +229,7 @@ private <T> ImmutableList<T> withList(List<T> items)
                 return this.of(items.get(0), items.get(1), items.get(2), items.get(3), items.get(4), items.get(5), items.get(6), items.get(7), items.get(8), items.get(9));
 
             default:
-                return ImmutableArrayList.newListWith((T[]) items.toArray());
+                return ImmutableArrayList.newList(items);
         }
     }
 

diff --git a/unit-tests/src/test/java/org/eclipse/collections/impl/list/mutable/FastListTest.java b/unit-tests/src/test/java/org/eclipse/collections/impl/list/mutable/FastListTest.java
@@ -24,6 +24,7 @@
 import org.eclipse.collections.api.block.function.Function0;
 import org.eclipse.collections.api.block.predicate.Predicate2;
 import org.eclipse.collections.api.block.procedure.Procedure;
+import org.eclipse.collections.api.list.ImmutableList;
 import org.eclipse.collections.api.list.MutableList;
 import org.eclipse.collections.api.set.MutableSet;
 import org.eclipse.collections.api.tuple.Twin;
@@ -1203,6 +1204,15 @@ public void testWith()
                 FastList.newListWith(42).withAll(Interval.from(10).to(12).toList()));
     }
 
+    @Test
+    public void unoptimizedListToImmutable()
+    {
+        FastList<String> list = FastList.newListWith(
+                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15");
+        ImmutableList<String> immutableList = list.toImmutable();
+        Verify.assertIterablesEqual(immutableList, list);
+    }
+
     @Test(expected = NoSuchElementException.class)
     public void min_empty_throws_without_comparator()
     {