1. 前言

• 前文我们先后用单向循环链表，环形数组来模拟了队列. 队列的特点是先进先出. 队头移除元素，队尾添加元素. 所以需要两个指针控制.
• 本文我们接下来提及如果和单向链表来模拟栈. 栈的特点是后进先出. 在栈顶压栈或弹栈. 另一侧不动的是栈底. 我们可以初始化哨兵节点，自哨兵节点之后对元素进行压栈弹栈操作.(即压栈操作是头插法)

2. 单向链表模拟栈

(1). 栈接口

public interface stack<E> {//压栈boolean push(E value);//弹栈, 栈非空返回栈顶元素E pop();//返回栈顶元素, 但不弹栈E peek();//判断栈是否为空boolean isEmpty();//判断栈是否已满boolean isFull();
}

(2). 单向链表模拟栈

//单向链表模拟栈
public class LinkedListStack<E> implements stack<E>, Iterable<E>{//链表的容量private int capacity;//栈的实际大小, 成员变量默认值是0private int size;Node<E> dummy;public LinkedListStack() {//初始化头节点dummy = new Node<>(null, null);}public LinkedListStack(int capacity) {this();this.capacity = capacity;}private static class Node<E> {Node<E> next;E value;public Node(Node<E> next, E value) {this.next = next;this.value = value;}}@Overridepublic boolean push(E value) {//如果栈满, 则不能添加元素if (isFull()) {return false;}Node<E> p = new Node<>(dummy.next, value);dummy.next = p;size++;return true;}@Overridepublic E pop() {//如果栈空, 则弹栈失败if(isEmpty()) {return null;}Node<E> p = dummy.next;dummy.next = p.next;size--;return p.value;}@Overridepublic E peek() {if(isEmpty()) {return null;}return dummy.next.value;}@Overridepublic boolean isEmpty() {return size == 0;}@Overridepublic boolean isFull() {return size == capacity;}@Overridepublic Iterator<E> iterator() {return new Iterator<E>() {Node<E> p = dummy.next;@Overridepublic boolean hasNext() {return p != null;}@Overridepublic E next() {E value = p.value;p = p.next;return value;}};}
}

3. 单元测试

public class LinkedListStackTest {@Testpublic void test1() {LinkedListStack<Integer> stack = new LinkedListStack<>(10);stack.push(1);stack.push(2);stack.push(3);stack.push(4);stack.push(5);stack.push(6);stack.push(7);for (Integer element : stack) {System.out.print(element + " ");}//7 6 5 4 3 2 1}@Testpublic void test2() {LinkedListStack<Integer> stack = new LinkedListStack<>(10);stack.push(1);stack.push(2);stack.push(3);stack.push(4);stack.push(5);stack.push(6);stack.push(7);//7, 输出栈顶元素, 但不弹栈, 输出7System.out.println(stack.peek());//7, 输出栈顶元素, 同时弹栈, 所以弹出7System.out.println(stack.pop());//6System.out.println(stack.peek());}
}