stack.java

来自「Java程序设计技巧与开发实例附书源代码。」· Java 代码 · 共 48 行

public class Stack
{
    private Node top;
    public Stack()
    {
        top = null;
    }

    public void push(Object obj)
    {
        Node node = new Node(obj);
        node.next = top;
        top = node;
    }

    public Object pop() throws StackException
    {
        if (top == null)
        {
            throw new StackException("popping from an empty stack");
        }
        else
        {
            Object obj = top.data;
            top = top.next;
            return obj;
        }
    }

    public Object peek() throws StackException
    {
        if (top == null)
        {
            throw new StackException("peeking into empty stack");
        }
        else
        {
            return top.data;
        }
    }

    public boolean isEmpty()
    {
        return (top == null);
    }
}