@SuppressWarnings("unchecked") not working with drag and drop

Question

I am using the following code that I found (How can I use Drag-and-Drop in Swing to get file path? from ABika) to do drag and drop:

final class FileDropHandler extends TransferHandler {
    @Override
    public boolean canImport(TransferHandler.TransferSupport support) {
        for (DataFlavor flavor : support.getDataFlavors()) {
            if (flavor.isFlavorJavaFileListType()) {
                return true;
            }
        }
        return false;
    }

    @Override
    @SuppressWarnings("unchecked")
    public boolean importData(TransferHandler.TransferSupport support) {
        if (!this.canImport(support))
            return false;

        List<File> files;
        try {
            files = (List<File>) support.getTransferable()
                    .getTransferData(DataFlavor.javaFileListFlavor);
        } catch (UnsupportedFlavorException | IOException ex) {
            // should never happen (or JDK is buggy)
            return false;
        }

        for (File file: files) {
            // do something...
        }
        return true;
    }
}

The handler is then added to a component.

But the problem is that despite the "@SuppressWarnings("unchecked")", I am getting an error:

The type List is not generic; it cannot be parameterized with arguments < File>

Can anyone tell me what is wrong here? It seems so straight-forward. Thanks

Answer 1

The method getTransferData is supposed to return a java.util.List in this case but you are importing java.awt.List, either as a single-type import statement i.e. import java.awt.List; or as an import-on-demand statement i.e. import java.awt.*;. If you have the former, you need to change it to java.util.List and if you have the latter, you need to import every class from java.awt as a single-type import instead, or use a qualified List type name in the importData method, like java.util.List<File>.