OAK-11584 : add getLast() method in IteratorUtils (#2188)

* OAK-11584: add getLast() method in IteratorUtils

* OAK-11584: add test cases for getLast()

Author: t-rana

oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/collections/IteratorUtils.java

@@ -208,4 +208,26 @@ public static <T> T get(Iterator<T> iterator, int index) {
         Objects.requireNonNull(iterator, "Iterator must not be null");
         return org.apache.commons.collections4.IteratorUtils.get(iterator, index);
     }
+
+    /**
+     * Returns the last element in the given iterator.
+     * <p>
+     * This method consumes the entire iterator to find the last element.
+     * <p>
+     *
+     * @param <T>      the type of elements in the iterator
+     * @param iterator the iterator to get the last element from, must not be null
+     * @return the last element in the iterator
+     * @throws NullPointerException   if the iterator is null
+     * @throws NoSuchElementException if the iterator is empty
+     */
+    public static <T> T getLast(Iterator<T> iterator) {
+        Objects.requireNonNull(iterator, "Iterator must not be null");
+        while (true) {
+            T currentElement = iterator.next();
+            if (!iterator.hasNext()) {
+                return currentElement;
+            }
+        }
+    }
 }

oak-commons/src/test/java/org/apache/jackrabbit/oak/commons/collections/IteratorUtilsTest.java

@@ -365,4 +365,53 @@ public String toString() {
         TestObject result = IteratorUtils.get(data.iterator(), 1);
         Assert.assertEquals("obj2", result.toString());
     }
+
+    @Test
+    public void testGetLastWithMultipleElements() {
+        Iterator<String> iterator = Arrays.asList("one", "two", "three").iterator();
+        Assert.assertEquals("three", IteratorUtils.getLast(iterator));
+        Assert.assertFalse(iterator.hasNext());
+    }
+
+    @Test
+    public void testGetLastWithSingleElement() {
+        Iterator<Integer> intIterator = List.of(1).iterator();
+        Assert.assertEquals(Integer.valueOf(1), IteratorUtils.getLast(intIterator));
+        Assert.assertFalse(intIterator.hasNext());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void testGetLastWithNullIterator() {
+        IteratorUtils.getLast(null);
+    }
+
+    @Test(expected = NoSuchElementException.class)
+    public void testGetLastWithEmptyIterator() {
+        IteratorUtils.getLast(Collections.emptyIterator());
+    }
+
+    @Test
+    public void testGetLastWithDifferentTypes() {
+        class TestObject {
+            private final String value;
+
+            TestObject(String value) {
+                this.value = value;
+            }
+
+            @Override
+            public boolean equals(Object o) {
+                if (this == o) return true;
+                if (o == null || getClass() != o.getClass()) return false;
+                TestObject that = (TestObject) o;
+                return value.equals(that.value);
+            }
+        }
+
+        TestObject obj1 = new TestObject("first");
+        TestObject obj2 = new TestObject("last");
+        Iterator<TestObject> objectIterator = Arrays.asList(obj1, obj2).iterator();
+        Assert.assertEquals(obj2, IteratorUtils.getLast(objectIterator));
+        Assert.assertFalse(objectIterator.hasNext());
+    }
 }