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); }}/* 輸出After pushing 5 elements: [4, 3, 2, 1, 0]Popped element = 4After popping 1 element : [3, 2, 1, 0]Peeked element = 3After peeking 1 element : [3, 2, 1, 0]*/