栈：链式栈

链式栈即底层通过链表实现的栈，本文所用到的链表是之前实现单链表

https://www.jianshu.com/p/9988a5df88ca

时间复杂度
入栈：O(1)
出栈：O(1)

接口类：

public interface Stack {

    int getSize();
    boolean isEmpty();
    void push(E e);
    E pop();
    E peek();

}

实现类：

public class LinkedListStack implements Stack {

    LinkedList list = new LinkedListImpl<>();
    @Override
    public int getSize() {
        return list.size();
    }

    @Override
    public boolean isEmpty() {
        return list.isEmpty();
    }

    @Override
    public void push(E e) {
      list.addFirst(e);
    }

    @Override
    public E pop() {
        return list.removeFirst();
    }

    @Override
    public E peek() {
        return list.get(0);
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder("top ");
        res.append(list);

        return res.toString();
    }
}

测试：

public class Main {

    public static void main(String[] args) {



        Stack stack = new LinkedListStack<>();

        for (int i = 0 ; i < 10 ; i++){
            stack.push(i);
            System.out.println(stack);
        }
        for (int i = 0; i < 10 ; i++){
            stack.pop();
            System.out.println(stack);
        }

    }
}

image.png