Java Stack 类

import java.util.*;

public class StackDemo {

static void showpush(Stack<Integer> st,int a) {
    st.push(new Integer(a));
    System.out.println("push(" + a + ")");
    System.out.println("stack: " + st);
}

static void showpop(Stack<Integer> st) {
    System.out.print("pop -> ");
    Integer a = (Integer) st.pop();
    System.out.println(a);
    System.out.println("stack: " + st);
}

public static void main(String[] args) {
    Stack<Integer> st = new Stack<Integer>();
    System.out.println("stack: " + st);
    showpush(st, 42);
    showpush(st, 66);
    showpush(st, 99);
    showpop(st);
    showpop(st);
    showpop(st);
    try {
        showpop(st);
    } catch (EmptyStackException e) {
        System.out.println("empty stack");
    }
}

}