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());
    }
}