Concurrency Pattern: Object that switches between Blocking and Non-Blocking Under Certain Conditions
private AtomicBoolean mSyncMode;
private AtomicBoolean mOutOfAsyncZone;
private AtomicInteger mAsyncThreads;

public MyObject()
{
    mSyncMode.set(false);
    mOutOfAsyncZone.set(false);
    mAsyncThreads=0;
}

//this method must always run synchronized...
public synchronized void SyncMethod()
{
    if(!mSyncMode.get())
        SetSyncMode(true);

    if(mSyncThreads > 0)
        wait();

    //do stuff....

    SetSyncMode(false);
}

//this method is used to toggle this object between sync and async mode.
public void SetSyncMode(boolean b)
{
    mSyncMode.set(b);
}

public void DoStuff()
{
    //do stuff...
}

public void DoOtherStuff()
{

}

//this method can run safely
public void SyncAndAsyncMethod()
{
    if(mSyncMode.get())
    {
        synchronized(this)
        {
            if(mAsyncThreads > 0)
                wait();

            DoStuff();
        }
    }
    else
    {
        mAsyncThreads++;
        DoStuff();
        mAsyncThreads--;

        if(mSyncMode.get() && mAsyncThreads <= 0)
        {
            synchronized(this)
            {
                notifyAll();
            }
        }
    }
}