Java collections

list.forEach(System.out::print);

Array

int[] a = new int[5];

a[0] = 1;
a[1] = 2;
a[2] = 4;
a[3] = 8;
a[4] = 16;

String => array with .split() & .join()

ArrayList

ordered, index based, dyn sizing, non sync, duplicates allowed

//Non-generic arraylist - NOT RECOMMENDED !!
ArrayList list = new ArrayList();

//Generic Arraylist with default capacity(=16)
List<Integer> numbers = new ArrayList<>(); 

//Generic Arraylist with the given capacity
List<Integer> numbers = new ArrayList<>(6); 

//Generic Arraylist initialized with another collection
List<Integer> numbers = new ArrayList<>( Arrays.asList(1,2,3,4,5) ); 

List<Integer> numbers = new ArrayList<>(6); 
numbers.add(1);

ArrayList<String> charList = new ArrayList<>(Arrays.asList(("A", "B", "C"));
String aChar = alphabetsList.get(0);

ArrayList<Integer> digits = new ArrayList<>(Arrays.asList(1,2,3,4,5,6));

Iterator<Integer> iterator = digits.iterator();

while(iterator.hasNext()) 
{
    System.out.println(iterator.next());
}
for(int i = 0; i < digits.size(); i++) 
{
    System.out.print(digits.get(i));
}
for(Integer d : digits) 
{
    System.out.print(d);
}

sorting

public class AgeSorter implements Comparator<Employee> 
{
    @Override
    public int compare(Employee e1, Employee e2) {
        //comparison logic
    }
}

link: https://howtodoinjava.com/java-collections/