How to Delete elements from the bottom of Stack in Java?

I understand your problem and easiest solution for this is to use remove(int i) function. This takes int as a parameter,

Stack<Integer> = new Stack<>();
//suppose stack is [1,2,3,4,5,6,7,8]

First use size() to get stack size. To delete first n/2 elements -

int size = (int) Math.floor(stack.size()/2)

Now, run a loop from 0 to size Be carefull always delete first element as every time stack gets updated

for(int i = 0; i<size ; i++) {
 stack.remove(0); 
}

Print the remaining stack

System.out.println(stack) //[5,6,7,8]

I hope this solves your doubt.

Based on your described use case, I think you need a different data structure.

I would recommend you to review the double-ended queue, or Deque, which has been part of the Java Collections API since Java 1.6.

This data structure is a bit of a hybrid between a Stack and a Queue, permitting you to add/remove elements to/from either end.

You can perform the traditional Stack operations of push and pop using addFirst and removeFirst, respectively.

To remove from the tail - or 'bottom' of the 'Stack', as you put it - you can use removeLast.

The size method will give you the number of elements.

You can use Deque in java. It supports both insertion and deletion on both sides. e.g.

Deque<Integer> deque = new ArrayDeque<>(Arrays.asList(1,2,3,4));
int count = deque.size() / 2;
while (count > 0)
{
  deque.removeLast();
  count--;
}

You can use linkedList as implementation of Deque instead. The difference between LinkedList and ArrayDeque: https://stackoverflow.com/questions/6163166/why-is-arraydeque-better-than-linkedlist#:~:text=Key%20differences%3A,LinkedList%20but%20not%20in%20ArrayDeque&text=The%20LinkedList%20implementation%20consumes%20more%20memory%20than%20the%20ArrayDeque

More details at https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html