Stack

Stack: LIFO, 

the Stack is a deprecated interface we should use Deque interface. The implementation can use LinkedList or array

push, pop, peek, size(), isEmpty()

public static void main(String[] args){
    Deque<Integer> stack = new LinkedList<>() ;
    System.out.println(stack.size()); //0 empty stack size = 0
    stack.push(5);
    stack.push(3);
    System.out.println(stack.size()); //2
    System.out.println(stack.pop()); //3
    System.out.println(stack.peek()); //5
    System.out.println(stack.isEmpty()); //false
    System.out.println(stack.pop()); //5
    System.out.println(stack.isEmpty()); //true

}