预增量运算符是否是线程安全的？ [英] Is the pre-increment operator thread-safe?

问题描述

我正在用java制作一个相互竞争的汽车程序。每辆车都是一个单独的线程。

I'm making a program in java that races a few cars against each other. Each car is a separate thread.

当汽车完成比赛时，每个人都会调用此方法。我已经在不同的定时器速度下测试了这个方法，它似乎工作正常。但我确实意识到每个线程都在访问变量carsComplete，有时是在同一时间（至少在date命令给我的范围内）。

When cars complete the race, each one all calls this method. I've tested the method at varying timer speeds, and it seems to work fine. But I do realize that each thread is accessing the variable carsComplete, sometimes at the exact same time (at least at the scope the date command is giving me).

所以我的问题是：这个方法是线程安全的吗？

So my question is: is this method thread-safe?

 public static String completeRace()
 {
      Date accessDate = new Date();
      System.out.println("Cars Complete: " + carsComplete + " Accessed at " + accessDate.toString());
      switch(++carsComplete)
      {
           case 1: return "1st";
           case 2: return "2nd";
           case 3: return "3rd";
           default: return carsComplete + "th";    
      }
 }

推荐答案

否，你应该使用像 java.util.concurrent.atomic.AtomicInteger 这样的东西。看看它的 getAndIncrement（）方法。

No, you should be using something like java.util.concurrent.atomic.AtomicInteger. Look at its getAndIncrement() method.

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