記一次排它鎖和自旋鎖的簡單實現

• 定義一個lock介面

  public interface PutMessageLock {
      void lock();
  
      void unlock();
  }
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• 排它鎖實現

  • 使用java自帶的 ReentrantLock即可

  public class PutMessageReentrantLock implements PutMessageLock {
      private ReentrantLock putMessageNormalLock = new ReentrantLock(); // NonfairSync
  
      @Override
      public void lock() {
          putMessageNormalLock.lock();
      }
  
      @Override
      public void unlock() {
          putMessageNormalLock.unlock();
      }
  }
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• 自旋鎖實現

  • 使用 cas + 迴圈來實現

  public class PutMessageSpinLock implements PutMessageLock {
      //true: Can lock, false : in lock.
      private AtomicBoolean putMessageSpinLock = new AtomicBoolean(true);
  
      @Override
      public void lock() {
          boolean flag;
          do {
              flag = this.putMessageSpinLock.compareAndSet(true, false);
          }
          while (!flag);
      }
  
      @Override
      public void unlock() {
          this.putMessageSpinLock.compareAndSet(false, true);
      }
  }
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