LibGDX

LibGDX is a cross platform game development library that uses the Java language. You can write your Java code once and then deploy your creations to Android, iOS, Web and desktop. 

LibGDX itself is arguably the easiest to use game library out there and there and has very beginner friendly community, however, its use of Java makes it less powerful than Cocos or SFML when creating large or complex projects. If Java is your language of choice but you want the advantages of using a cross-platform library then LibGDX would be a good choice.