java 栈

package testjavapro;
import java.util.*;

public class testjava {
 
    static void showpush(Stack<Integer> st, int a) {
        st.push(new Integer(a));
        System.out.println("push(" + a + ")");
        System.out.println("cur stack: " + st);
    }
 
    static void showpop(Stack<Integer> st) {
        System.out.print("pop -> ");
        Integer a = (Integer) st.pop();
        System.out.println(a);
        System.out.println("cur 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");
        }
    }
}

stack: []
push(42)
cur stack: [42]
push(66)
cur stack: [42, 66]
push(99)
cur stack: [42, 66, 99]
pop -> 99
cur stack: [42, 66]
pop -> 66
cur stack: [42]
pop -> 42
cur stack: []
pop -> empty stack