Array:

Simple fixed sized arrays that we create in Java, like below

      int arr[] = new int[10]

ArrayList :

Dynamic sized arrays in Java that implement List interface.

      ArrayList<Type> arrL = new ArrayList<Type>();

  Here Type is the type of elements in ArrayList to
  be created

• An array is basic functionality provided by Java. ArrayList is part of collection framework in Java. Therefore array members are accessed using [], while ArrayList has a set of methods to access elements and modify them.
• Array is a fixed size data structure while ArrayList is not. One need not to mention the size of Arraylist while creating its object. Even if we specify some initial capacity, we can add more elements.
• Array can contain both primitive data types as well as objects of a class depending on the definition of the array. However, ArrayList only supports object entries, not the primitive data types. Note: When we do arraylist.add(1); : it converts the primitive int data type into an Integer object.
• Since ArrayList can’t be created for primitive data types, members of ArrayList are always references to objects at different memory locations (See this for details). Therefore in ArrayList, the actual objects are never stored at contiguous locations. References of the actual objects are stored at contiguous locations. In array, it depends whether the arrays is of primitive type or object type. In case of primitive types, actual values are contiguous locations, but in case of objects, allocation is similar to ArrayList.
• http://www.geeksforgeeks.org/array-vs-arraylist-in-java/