linkedstack.java

真的很麻烦也

public class LinkedStack implements Stack {
  private Node top;		// reference to the head node
  private int size;		// number of elements in the stack   
  public LinkedStack() {	// initializes an empty stack
    top = null;
    size = 0;
  }
  public int size() {
    return size;
  }
  public boolean isEmpty() {
    if (top == null)
      return true;
    return false;
  }
  public Object push(Object elem) {
    Node v = new Node();	// create a new node
    v.setElement(elem);
    v.setNext(top);		// link-in the new node
    top = v;
    size++;
    return ("-");
  }
  public Object top() //throws StackEmptyException 
  {
    if (isEmpty())
		{
			return ("Stack is empty.");
		}
     // throw new StackEmptyException("Stack is empty.");
    return top.getElement();
  }
  public Object pop() //throws StackEmptyException 
  {
    if (isEmpty())
    {
		return ("Stack is empty.");
	}
    //  throw new StackEmptyException("Stack is empty.");
    Object temp = top.getElement();
    top = top.getNext();	// link-out the former top node
    size--;
    return temp;
  }
  
  public String getContent()
	{
		String cont= "";
		if (size == 0)
		 	return cont;
		Node CurNode = top;
		for (int i =1; i<=size; i++ )
		{
			cont += (CurNode.getElement() + ",");
			CurNode = CurNode.getNext();

		}
		
		return (cont.substring(0,cont.length()-1));
	}
}