安全地使用 Java 映射作为互斥锁持有者

Question

要求是，方法 A 中的相关代码不能在任何具有相同类的 Object 上并行执行。

下面的伪代码能做到吗？

 private final Map<String, Object> simpleMutex = new HashMap<>();
 
 public void A( final Object o)
  {
    final ThreadLocal<Object> myLock = new ThreadLocal<>();
    synchronized ( simpleMutex )
    {
      myLock.set( simpleMutex.computeIfAbsent( o.getClass().getName(), className-> new Object() ) );
    }

    synchronized ( myLock.get() )
    {
      System.out.println("Executing A on " + o);
    }
  }

Answer 1

private final Map<Class<?>, Object> locksMap = new ConcurrentHashMap<>();

public void A(final Object o) {
     Object myLock = locksMap.computeIfAbsent(o.getClass(), className -> new Object());
     synchronized (myLock) {
          System.out.println("Executing A on " + o);
     }
}