Array has length property which provides the length of the Array or Array object. It is the total space allocated in memory during the initialization of the array. Array is static so when we create an array of size n then n blocks are created of array type and JVM initializes every block by default value. Let’s see this in the following figure. 
On the other hand, java ArrayList does not have length property. The java ArrayList has size() method for ArrayList which provides the total number of objects available in the collection.
We use length property to find length of Array in Java and size() to find size of ArrayList.
Below is the implementation of the above idea:
Java
// Java code to illustrate the difference between// length in java Array and size in ArrayListimport java.util.ArrayList;public class GFG { // main method public static void main(String[] args) { /* creating an array A[] for 10 elements */ String A[] = new String[10]; /* store 2 elements */ A[0] = "Hello"; A[1] = "Geeks!"; /* print length of array A[] */ System.out.println(A.length); // 10 /* Creating an ArrayList */ ArrayList<String> al = new ArrayList<String>(); /* add 3 elements */ al.add("G"); al.add("F"); al.add("G"); /* print size of ArrayList */ System.out.println(al.size()); // 3 }} |
Output:
10 3
