Slightly revived and updated repository of JTileDownloader, a very old tool to download all tiles in a bounding box. Its user agent is banned on OSM tile servers, so you would need to recompile to use it.
Please always make sure that you agree and stick to the policies of the tile-providers before downloading!
Please take a look at the Tile usage policy of OpenStreetMap.
Copyright © 2008-2020, Friedrich Maier, Sven Strickroth, Ilya Zverev