JAVA高级面试进阶训练营视频教程

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1.解决方法

Executors.newSingleThreadExecutor()取得的Executor实例有以下特性:
任务顺序执行. 比如：
executor.submit(task1);
executor.submit(task2);
必须等task1执行完，task2才能执行。
task1和task2会被放入一个队列里，由一个工作线程来处理。即：一共有2个线程(主线程、处理任务的工作线程）。

 

以上如果是单机可以解决,如果是多台服务器的话,仍然还是会存在并发的问题.

或者使用mysql数据库修改的特性,update排序依次来修改,增加否决字段,修改的时候带上条件值,可以解决并发问题.(多个租客租时间段重叠的同一辆车且自动接单,这个情况就很明显凸现出来.)

2.测试代码

/**
 * 
 */
package mock;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

import com.autoyolConsole.util.esb.HttpUtils;

/**
 * @author xxx
 * @function 
 * @date 2016年3月15日
 * @version 1.0
 */
public class ConcurrentTest2 {
    private static int thread_num = 5;
    private static int client_num = 20;
    private static final String reqUrl = "http://10.0.3.213:7064/";
    private static String url = "tranxx/vxx/reqx";
    
    private static String[] tokens = new String[]{"4dafe25e1f8f4e368834f95b75030193","6a3d3702cccf46a3b94e2c805a16c0a3","a4ee5ad888714a9e9d0d4646e725495b","9adbecae26f648dea2767e8d908463dd","20910b477f0142f6b7f709babcdafb72",
        "c3c53c987256422a8667a455a1cd1117","efb1f941eab440619d8a339f2fafa429","786a901fe5414d14894ca4db738efe2f","8fbad92b9a7c4d4b8a420db23c405e49","75992aa62eb947739f0bfc8a83234584",
        "aa110a58ade241a3b456b8be5ddd2551","aa110a58ade241a3b456b8be5ddd255a","aa110a58ade241a3b456b8be5ddd2552","aa110a58ade241a3b456b8be5ddd2553","aa110a58ade241a3b456b8be5ddd2554",
        "aa110a58ade241a3b456b8be5ddd2555","aa110a58ade241a3b456b8be5ddd2556","aa110a58ade241a3b456b8be5ddd2557","aa110a58ade241a3b456b8be5ddd2558","aa110a58ade241a3b456b8be5ddd2559"};
    
    private static String[] mobiles = new String[]{"197xxxx9705","199xxxx5297","199xxxx8606","198xxxx9898","197xxxx1330",
        "197xxxx9999","193xxxx2233","193xxxx2345","191xxxx6712","198xxxx6852",
        "191xxxx6820","987xxxx0296","190xxxx7589","199xxxx8888","193xxxx2312",
        "199xxxx5496","161xxxx3280","190xxxx1082","199xxxx3724","199xxxx0537"};
    
    public static void main(String[] args) {
        ExecutorService exec = Executors.newCachedThreadPool();
        // thread_num个线程可以同时访问
        final Semaphore semp = new Semaphore(thread_num);
        // 模拟client_num个客户端访问
        for (int index = 0; index < client_num; index++) {
            final int NO = index;
            Runnable run = new Runnable() {
                public void run() {
                    try {
                        // 获取许可
                        semp.acquire();
                        
                        System.out.println("Thread并发事情>>>"+ NO);
                        
                        String strReq = "{\"carNo\":\"303473636\",\"token\":\""+tokens[NO]+"\",\"conPhone\":\""+mobiles[NO]+"\","
                                + "\"rentTime\":\"20160519183000\",\"revertTime\":\"20160522183000\",\"rentReason\":\"上下班用车\",\"oilType\":\"1\",\"disCouponIds\":\"0\",\"useBal\":\"0\",\"source\":\"3\",\"rentCity\":\"本市\"}";
                        
                        try {
                            String result = HttpUtils.appPost(strReq, reqUrl+ url);
                            System.err.println("接口调用返回结果：" + result);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        
                        semp.release();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            };
            exec.execute(run);
        }
        // 退出线程池
        exec.shutdown();
    }
}