十三 用链表实现栈

package com.lt.datastructure.stackqueue;
/*
 * 使用链表实现栈
 */
public class LinkedListStack<E> implements Stack<E> {
    LinkedList<E> list;
    LinkedListStack(){
        list = new LinkedList<>();
    }
    
    @Override
    public int getsize() {
        return list.getSize();
    }
    
    @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.getFirst();
    }
    
    @Override
    public String toString() {
       StringBuilder res = new  StringBuilder();
       //栈顶
       res.append("Stack:top  ");
       res.append(list);
       
       return res.toString();
    }
    
    public static void main(String[] args) {
        LinkedListStack<Integer> stack = new LinkedListStack<>();
        for(int i=0; i<5; i++){
            stack.push(i);
            System.out.println(stack);
        }
        stack.pop();
        System.out.println("pop: \n"+stack);
    }
}

package com.lt.datastructure.stackqueue;

import java.util.Random;

public class Main {

    // 测试使用stack运行opCount个push和pop操作所需要的时间，单位：秒
    private static double testStack(Stack<Integer> stack, int opCount){

        long startTime = System.nanoTime();

        Random random = new Random();
        for(int i = 0 ; i < opCount ; i ++)
            stack.push(random.nextInt(Integer.MAX_VALUE));
        for(int i = 0 ; i < opCount ; i ++)
            stack.pop();

        long endTime = System.nanoTime();

        return (endTime - startTime) / 1000000000.0;
    }

    public static void main(String[] args) {

        int opCount = 100000;

        ArrayStack<Integer> arrayStack = new ArrayStack<>();
        double time1 = testStack(arrayStack, opCount);
        System.out.println("ArrayStack, time: " + time1 + " s");

        LinkedListStack<Integer> linkedListStack = new LinkedListStack<>();
        double time2 = testStack(linkedListStack, opCount);
        System.out.println("LinkedListStack, time: " + time2 + " s");

        // 其实这个时间比较很复杂，因为LinkedListStack中包含更多的new操作
    }
}