Need of apache commons for collections

CollectionsWithoutNullCheck.java

package com.knoldus;

import java.util.ArrayList;
import java.util.stream.Collectors;

public class LambdaEx {

    public static void main(String[] args) {
        ArrayList<String> list1 = null;
        list1.stream().map(elem -> elem + "Knoldus").collect(Collectors.toList());
        
        list1.forEach(System.out::println);
    }
}