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
     
       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 }