高併發計數器

package day01.synchronize;

/**

• @title: Counter
• @description:
• @author: 北京小桔匯金網絡科技有限公司
• @date: 2018/5/2 13:35 */ import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicInteger;

/**

• 關於count++在多線程調用狀況下

• @author jan / public class Counter { // private volatile int count = 0; private AtomicInteger count = new AtomicInteger(1); /*

  • 爲了保證數據的準確性，多線程的狀況下須要加上synchronized關鍵字</br>
  • 不然會出現出乎預料的結果 這也是線程安全的重要體現 */ public void increment() { count.incrementAndGet(); }

  private int getCount() { return count.get(); }

  /**

  • 這裏模擬一個遞增的任務，遞增目標爲100W */ public static void main(String[] args) throws InterruptedException { final Counter counter = new Counter(); // final AtomicCounter counter = new AtomicCounter(); int workCount = 1000000; ExecutorService executor = Executors.newFixedThreadPool(10); long start = System.currentTimeMillis(); for (int i = 0; i < workCount; i++) { Runnable runnable = new Runnable() { @Override public void run() { counter.increment(); } }; executor.execute(runnable); } // 關閉啓動線程，執行未完成的任務 executor.shutdown(); // 等待全部線程完成任務，完成後才繼續執行下一步 executor.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS); System.out.println("耗時：" + (System.currentTimeMillis() - start) + "ms"); System.out.println("執行結果：count=" + counter.getCount()); } }