add static intersection method for sorted lists

primitiveCollections/src/test/java/org/lucares/collections/IntListTest.java

@@ -1032,4 +1032,31 @@ public class IntListTest {
 		list.replaceAll(v -> 2); // replace all with 2 -> [2,2,2,2]
 		Assert.assertFalse("unsorted list stays unsorted", list.isSorted());
 	}
+
+	@Test
+	public void testIntersectionSortedLists() {
+		{
+			final IntList a = IntList.of(0, 1, 2, 3, 4);
+			final IntList b = IntList.of(2, 4, 5);
+			final IntList actual = IntList.intersection(a, b);
+			Assert.assertEquals(IntList.of(2, 4), actual);
+		}
+
+		/*
+		 * cardinality of elements that occur multiple time is equal to the minimum
+		 * cardinality in either list
+		 */
+		{
+			final IntList a = IntList.of(3, 3, 3);
+			final IntList b = IntList.of(3, 3);
+			final IntList actual = IntList.intersection(a, b);
+			Assert.assertEquals(IntList.of(3, 3), actual);
+		}
+		{
+			final IntList a = IntList.of(4);
+			final IntList b = IntList.of(4, 4, 4);
+			final IntList actual = IntList.intersection(a, b);
+			Assert.assertEquals(IntList.of(4), actual);
+		}
+	}
 }