NestedIterator: adjust javadoc, add tests

Author: andrei-punko

src/main/java/by/andd3dfx/iterators/NestedIterator.java

@@ -10,10 +10,10 @@
  * <pre>
  * <a href="https://leetcode.com/problems/flatten-nested-list-iterator/description/">Task description</a>
  *
- * You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists. Implement an iterator to flatten it.
+ * You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers
+ * or other lists. Implement an iterator to flatten it.
  *
  * Implement the NestedIterator class:
- *
  *     NestedIterator(List<NestedInteger> nestedList) Initializes the iterator with the nested list nestedList.
  *     int next() Returns the next integer in the nested list.
  *     boolean hasNext() Returns true if there are still some integers in the nested list and false otherwise.

src/test/java/by/andd3dfx/iterators/NestedIteratorTest.java

@@ -6,6 +6,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.NoSuchElementException;
 import org.junit.Test;
 
 public class NestedIteratorTest {
@@ -24,13 +25,22 @@ public void testNextAndHasNext() {
                 new NestedIntegerList(new NestedInteger(4), new NestedIntegerList(6))
             ),
             List.of(1, 4, 6));
+    }
 
+    @Test
+    public void testNextAndHasNext_emptyList() {
         check(List.of(
                 new NestedIntegerList()
             ),
             List.of());
     }
 
+    @Test(expected = NoSuchElementException.class)
+    public void testNextWhenNoElements() {
+        var nestedIterator = new NestedIterator(List.of());
+        nestedIterator.next();
+    }
+
     private void check(List<INestedInteger> incoming, List<Integer> outgoing) {
         var result = new ArrayList<>();