use 'sorted' flag in indexOf

primitiveCollections/src/main/java/org/lucares/collections/IntList.java

@@ -566,12 +566,20 @@ public final class IntList implements Serializable, Cloneable {
 	 *             if offset is negative, or larger than the size of the list
 	 */
 	public int indexOf(final int value, final int offset) {
-		for (int i = offset; i < index; i++) {
-			if (data[i] == value) {
-				return i;
+
+		int result = -1;
+		if (sorted) {
+			final int insertionPoint = Arrays.binarySearch(data, offset, size(), value);
+			result = insertionPoint < 0 ? -1 : insertionPoint;
+		} else {
+			for (int i = offset; i < index; i++) {
+				if (data[i] == value) {
+					result = i;
+					break;
+				}
 			}
 		}
-		return -1;
+		return result;
 	}
 
 	@Override

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

@@ -604,7 +604,7 @@ public class IntListTest {
 	}
 
 	@Test
-	public void testIndexOf() {
+	public void testIndexOfOnSortedList() {
 		final IntList list = new IntList();
 		Assert.assertEquals(-1, list.indexOf(0));
 
@@ -619,7 +619,28 @@ public class IntListTest {
 	}
 
 	@Test
-	public void testIndexOfWithOffset() {
+	public void testIndexOfOnUnsortedList() {
+		final IntList list = IntList.of(2, 0, 1);
+		Assert.assertEquals(1, list.indexOf(0));
+
+		Assert.assertEquals(0, list.indexOf(2));
+		Assert.assertEquals(2, list.indexOf(1));
+		Assert.assertEquals(-1, list.indexOf(3));
+	}
+
+	@Test
+	public void testIndexOfWithOffsetOnSortedList() {
+		final IntList list = new IntList();
+		list.addAll(1, 1, 2, 3, 3);
+		Assert.assertEquals(0, list.indexOf(1, 0));
+		Assert.assertEquals(1, list.indexOf(1, 1));
+		Assert.assertEquals(2, list.indexOf(2, 2));
+		Assert.assertEquals(-1, list.indexOf(2, 3));
+		Assert.assertEquals(3, list.indexOf(3, 2));
+	}
+
+	@Test
+	public void testIndexOfWithOffsetOnUnsortedList() {
 		final IntList list = new IntList();
 		list.addAll(0, 2, 0, 2);
 		Assert.assertEquals(1, list.indexOf(2, 0));