import java.util.ArrayDeque;
import java.util.Deque;
public class IntegerStack {
 private Deque<Integer> data = new ArrayDeque<Integer>();
 public void push(Integer element) {
  data.addFirst(element);
 }
 public Integer pop() {
  return data.removeFirst();
 }
 public Integer peek() {
  return data.peekFirst();
 }
 public String toString() {
  return data.toString();
 }
 public static void main(String[] args) {
  IntegerStack stack = new IntegerStack();
  for (int i = 0; i < 5; i++) {
   stack.push(i);
  }
  System.out.println("After pushing 5 elements: " + stack);
  int m = stack.pop();
  System.out.println("Popped element = " + m);
  System.out.println("After popping 1 element : " + stack);
  int n = stack.peek();
  System.out.println("Peeked element = " + n);
  System.out.println("After peeking 1 element : " + stack);
 }
}
/* 输出
After pushing 5 elements: [4, 3, 2, 1, 0]
Popped element = 4
After popping 1 element : [3, 2, 1, 0]
Peeked element = 3
After peeking 1 element : [3, 2, 1, 0]
*/