Add link to official ArrayList documentation (#19787)

guide/english/java/arraylist/index.md

@@ -67,3 +67,6 @@ Since ArrayList implements *List*, an ArrayList can be created using the followi
   An ArrayList allows us to randomly access elements. ArrayList is similar to *Vector* in a lot of ways. But it is faster than Vectors. The main thing to note is that - Vectors are faster than arrays but ArrayLists are not. 
   
   So when it comes down to choosing between the two - if speed is critical then Vectors should be considered, otherwise ArrayLists are better when it comes to storing large number of elements and accessing them efficiently.
+
+## More Information
+- [ArrayList Documentation](https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html)