Drag and Drop is a direct manipulation gesture found in many Graphical User Interface systems that provides a mechanism to transfer information between two entities logically associated with presentation elements in the GUI. Normally driven by a physical gesture of a human user using an appropriate input device, Drag and Drop provides both a mechanism to enable continuous feedback regarding the possible outcome of any subsequent data transfer to the user during navigation over the presentation elements in the GUI, and the facilities to provide for any subsequent data negotiation and transfer.

This package defines the classes and interfaces necessary to perform Drag and Drop operations in Java. It defines classes for the drag-source and the drop-target, as well as events for transferring the data being dragged. This package also provides a means for giving visual feedback to the user throughout the duration of the Drag and Drop operation.

A typical Drag and Drop operation can be decomposed into the following states (not entirely sequentially):

- A `DragSource` comes into existence, associated with some presentation element (`Component`) in the GUI, to initiate a Drag and Drop of some potentially `Transferable` data.
- 1 or more `DropTarget`(s) come into/go out of existence, associated with presentation elements in the GUI (Components), potentially capable of consuming `Transferable` data types.
- A `DragGestureRecognizer` is obtained from the `DragSource` and is associated with a `Component` in order to track and identify any Drag initiating gesture by the user over the `Component`.
- A user makes a Drag gesture over the `Component`, which the registered `DragGestureRecognizer` detects, and notifies its `DragGestureListener` of.

  Note: Although this API consistently refers to the stimulus for a drag and drop operation being a physical gesture by a human user, this does not preclude a programmatically driven DnD operation given the appropriate implementation of a `DragSource`. This package contains the abstract class `MouseDragGestureRecognizer` for recognizing mouse device gestures. Other abstract subclasses may be provided by the platform to support other input devices or particular `Component` class semantics.

- The `DragGestureListener` causes the `DragSource` to initiate the Drag and Drop operation on behalf of the user, perhaps animating the GUI Cursor and/or rendering an `Image` of the item(s) that are the subject of the operation.
- As the user gestures navigate over `Component`(s) in the GUI with associated `DropTarget`(s), the `DragSource` receives notifications in order to provide "Drag Over" feedback effects, and the `DropTarget`(s) receive notifications in order to provide "Drag Under" feedback effects based upon the operation(s) supported and the data type(s) involved.

The gesture itself moves a logical cursor across the GUI hierarchy, intersecting the geometry of GUI Component(s), possibly resulting in the logical "Drag" cursor entering, crossing, and subsequently leaving `Component`(s) and associated `DropTarget`(s).

The `DragSource` object manifests "Drag Over" feedback to the user, in the typical case by animating the GUI `Cursor` associated with the logical cursor.

`DropTarget` objects manifest "Drag Under" feedback to the user, in the typical case, by rendering animations into their associated GUI `Component`(s) under the GUI Cursor.

The determination of the feedback effects, and the ultimate success or failure of the data transfer, should one occur, is parameterized as follows:

- By the transfer "operation" selected by the user, and supported by both the `DragSource` and `DropTarget`: Copy, Move or Reference(link).
- By the intersection of the set of data types provided by the `DragSource` and the set of data types comprehensible by the `DropTarget`.
- When the user terminates the drag operation, normally resulting in a successful Drop, both the `DragSource` and `DropTarget` receive notifications that include, and result in the type negotiation and transfer of, the information associated with the `DragSource` via a `Transferable` object.

@since 1.2