Get extension from path in android

For find extension from a given path you can use any one from given solution:

Method 1: Get extension from string path

String path = "/storage/emulated/0/WhatsApp/Media/WhatsApp Video/VID-20190125-WA0010.mp4"; 
String extension = path.substring(path.lastIndexOf("."));

Method 2: Get an extension from the file

So in your case, it should be something like that

String path = "/storage/emulated/0/WhatsApp/Media/WhatsApp Video/VID-20190125-WA0010.mp4"; 
File file = new File(path);
String extension = file.getAbsolutePath().substring(file.getAbsolutePath().lastIndexOf("."));

Method 3:

You can use Utility Library of Android FilenameUtils.getExtension from Apache Commons IO-

String extension = FilenameUtils.getExtension("/storage/emulated/0/WhatsApp/Media/WhatsApp Video/VID-20190125-WA0010.mp4");