链式栈——Java实现

package struct;

//接口
interface ILinkStack{
	//栈中元素个数（栈大小）
	int size();
	//取栈顶元素
	Object top();
	//判断栈是否为空
	boolean isEmpty();
	//入栈
	Object pop();
	//出栈
	Object push(Object value);
	//清空栈
	void clear();
}

//工厂类
class Factory2{
	private Factory2(){}
	public static ILinkStack getILinkStackInstance(){
		return new LinkStackImpl();
	}
}

class LinkStackImpl implements ILinkStack {
	//栈顶元素
	Node top;
	//链表长度记录入栈元素
	private int count;
	class Node{
		Node prev;
		Node next;
		Object data;
		public Node(Object data) {
			this.data = data;
		}
	}
	
	public int size() {
		return count;
	}

	public Object top() {
		return top.data;
	}
	//判栈空
	public boolean isEmpty() {
		return (size()==0);
	}
	//入栈
	public Object push(Object value) {
		Node node = new Node(value);
		if(top == null){
			top = node;
		}else{
			top.next = node;
			node.prev = top;
			top = top.next;
		}
		count++;
		return top;
	}
	public void print(){
		System.out.println("从栈顶到栈底打印栈中元素：");
		myPrint(top);
		return;
	}
	//栈顶->栈底打印链表
	private void myPrint(Node top){
		for(Node node = top;node!=null;node=node.prev){
			System.out.print(node.data+" ");
		}
	}
	//出栈
	public Object pop() {
		Node node = top;
		if(top == null){
			System.out.println("空栈无要出栈元素");
			return -1;
		}else{
			top = top.prev;
			node.prev = null;
			node.data = null;
		}
		count--;
		return top();
	}
	//清空栈
	public void clear(){
		Node node1 = top;
		for(Node node = top;node!=null;){
			node = node.prev;
			node1.data = null;
			node1.prev = null;
			count--;
		} 
	}
}
public class LinkStack {
	public static void main(String[] args) {
		ILinkStack linkStack = Factory2.getILinkStackInstance();
		//向下转型
		LinkStackImpl linkStack1 = (LinkStackImpl)linkStack;
		System.out.println("============测试isEmpty函数(空栈)=================");
		System.out.println(linkStack.isEmpty());
		System.out.println("============测试push和print函数=================");
		linkStack.push(5);
		linkStack.push(9);
		linkStack.push(10);
		linkStack.push(1);
		linkStack.push(8);
		linkStack.push(12);
		linkStack.push(6);
		linkStack.push(3);
		linkStack1.print();
		System.out.println();
		System.out.println("============入栈后测试top函数=================");
		System.out.println(linkStack.top());
		System.out.println("============入栈后测试size函数=================");
		System.out.println(linkStack.size());
		System.out.println("============测试pop和print函数=================");
		linkStack.pop();
		linkStack.pop();
		linkStack.pop();
		linkStack1.print();
		System.out.println();
		System.out.println("============出站后测试top函数=================");
		System.out.println(linkStack.top());
		System.out.println("============出栈后测试size函数=================");
		System.out.println(linkStack.size());
		System.out.println("============测试clear后size函数=================");
		linkStack.clear();
		System.out.println(linkStack.size());
	}
}