import sun.lwawt.macosx.CDropTarget; //导入依赖的package包/类
@Override
public void addDropTarget(DropTarget dt) {
    LWWindowPeer winPeer = getWindowPeerOrSelf();
    if (winPeer != null && winPeer != this) {
        // We need to register the DropTarget in the
        // peer of the window ancestor of the component
        winPeer.addDropTarget(dt);
    } else {
        synchronized (dropTargetLock) {
            // 10-14-02 VL: Windows WComponentPeer would add (or remove) the drop target only
            // if it's the first (or last) one for the component. Otherwise this call is a no-op.
            if (++fNumDropTargets == 1) {
                // Having a non-null drop target would be an error but let's check just in case:
                if (fDropTarget != null)
                    System.err.println("CComponent.addDropTarget(): current drop target is non-null.");

                // Create a new drop target:
                fDropTarget = CDropTarget.createDropTarget(dt, target, this);
            }
        }
    }
}