fix bug

hutool-core/src/main/java/cn/hutool/core/collection/IterUtil.java

@@ -643,7 +643,7 @@ public class IterUtil {
 	 */
 	public static Class<?> getElementType(Iterator<?> iterator) {
 		final Iterator<?> iter2 = new CopiedIter<>(iterator);
-		if (iter2.hasNext()) {
+		while (iter2.hasNext()) {
 			final Object t = iter2.next();
 			if (null != t) {
 				return t.getClass();

hutool-core/src/test/java/cn/hutool/core/collection/IterUtilTest.java

@@ -90,6 +90,13 @@ public class IterUtilTest {
 		Assert.assertEquals(expectedMap, testMap);
 	}
 
+	@Test
+	public void getElementTypeTest(){
+		List<Integer> integers = Arrays.asList(null, 1);
+		Class<?> elementType = IterUtil.getElementType(integers);
+		Assert.assertEquals(Integer.class,elementType);
+	}
+
 	@Data
 	@AllArgsConstructor
 	public static class Car {