Returns the drag source's supported drop actions, when this TransferSupport represents a drop.

The source actions represent the set of actions supported by the source of this transfer, and are represented as some bitwise-OR combination of COPY, MOVE and LINK. You may wish to query this in TransferHandler's canImport method when determining the suitability of a drop or when deciding on a drop action to explicitly choose. To determine if a particular action is supported by the source, bitwise-AND the action with the source drop actions, and then compare the result against the original action. For example:

 boolean copySupported = (COPY & getSourceDropActions()) == COPY;

This method is only for use with drag and drop transfers. Calling it when isDrop() is false results in an IllegalStateException.

Returns: the drag source's supported drop actions

Exceptions:

IllegalStateException if this is not a drop