In Java, following are two different ways to create an array.

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

Differences between Array and ArrayList

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.

// A Java program to demonstrate differences between array
// and ArrayList
import java.util.ArrayList;
import java.util.Arrays;

class Test
{
public static void main(String args[])
{
/* ........... Normal Array............. */
int[] arr = new int[2];
arr[0] = 1;
arr[1] = 2;
System.out.println(arr[0]);

/*............ArrayList..............*/
// Create an arrayList with initial capacity 2
ArrayList<Integer> arrL = new ArrayList<Integer>(2);

// Add elements to ArrayList
arrL.add(1);
arrL.add(2);

// Access elements of ArrayList
System.out.println(arrL.get(0));
}
}
Output:

1
1
.

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.

// A Java program to demonstrate differences between array
// and ArrayList
import java.util.ArrayList;
import java.util.Arrays;
class Test
{
public static void main(String args[])
{
/* ........... Normal Array............. */
// Need to specify the size for array
int[] arr = new int[3];
arr[0] = 1;
arr[1] = 2;
arr[2] = 3;
// We cannot add more elements to array arr[]

/*............ArrayList..............*/
// Need not to specify size
ArrayList<Integer> arrL = new ArrayList<Integer>();
arrL.add(1);
arrL.add(2);
arrL.add(3);
arrL.add(4);
// We can add more elements to arrL

System.out.println(arrL);
System.out.println(Arrays.toString(arr));
}
}
Output:

[1, 2, 3, 4]
[1, 2, 3]
.

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. Sample Code:

import java.util.ArrayList;
class Test
{
public static void main(String args[])
{
// allowed
int[] array = new int[3];

// allowed, however, need to be initialized
Test[] array1 = new Test[3];

// not allowed (Uncommenting below line causes
// compiler error)
// ArrayList<char> arrL = new ArrayList<char>();

// Allowed
ArrayList<Integer> arrL1 = new ArrayList<>();
ArrayList<String> arrL2 = new ArrayList<>();
ArrayList<Object> arrL3 = new ArrayList<>();
}
}
.

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.
Java ArrayList supports many additional operations like indexOf(), remove(), etc. These functions are not supported by Arrays.
As a side note, ArrayList in Java can be seen as similar to vector in C++.