Array vs ArrayList in Java

Array is a fixed length data structure whereas ArrayList is a variable length Collection class. We cannot change length of array once created in Java but ArrayList can be changed.

We cannot store primitives in ArrayList, it can only store objects. But array can contain both primitives and objects in Java. Since Java 5, primitives are automatically converted in objects which is known as auto-boxing.

import java.util.*;
public class ListExample {
public static void main(String[] args) {
	List<Integer> list=new ArrayList<>();
	list.add(Integer.valueOf(10));//storing Integer object
	list.add(20);//Now compiler converts it into Integer.valueOf(20) which is object
	list.add(30);
	
	System.out.println("Traversing List...");
	for(Integer i:list){
		System.out.println(i);
	}
}
}

Output: