java如何实现一个实例栈？

今天在一家公司面试的时候，问了一道题。这道题直接就给我整蒙了。他问我在平时的工作中如何实现一个栈的实例？

额 就一个简单入栈出站就行吧，这个是一次入栈10 20 30 40 50 输出出栈顺序

class MyStack {
   private int maxSize;
   private long[] stackArray;
   private int top;
   public MyStack(int s) {
      maxSize = s;
      stackArray = new long[maxSize];
      top = -1;
   }
   public void push(long j) {
      stackArray[++top] = j;
   }
   public long pop() {
      return stackArray[top--];
   }
   public long peek() {
      return stackArray[top];
   }
   public boolean isEmpty() {
      return (top == -1);
   }
   public boolean isFull() {
      return (top == maxSize - 1);
   }
   public static void main(String[] args) {
      MyStack theStack = new MyStack(10); 
      theStack.push(10);
      theStack.push(20);
      theStack.push(30);
      theStack.push(40);
      theStack.push(50);
      while (!theStack.isEmpty()) {
         long value = theStack.pop();
         System.out.print(value);
         System.out.print(" ");
      }
      System.out.println("");
   }
}

是要自定义堆栈吗?