As I'm interested in creating games like Jetpack Joyride for mobile devices and so on, I wanted to know what technology was used to create the game.
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There are some options to release a game for both iOS and android:
Each of these ways has their own advantages and weaknesses. But I suggest you use one of existing gameengines, either cocos2d-x (if you are a coder by nature) or Unity (if you are a designer)
To answer your question directly, Jetpack Joyride was made in Objective-C, with possibly a few areas of low level being C++ (and OpenGL for 3d hardware interaction).
You cannot make Java apps on iOS (not without jailbreaking).
HTML5 apps are not available from the App Store.
iOS does not run Flash, though Adobe do provide the capabilities for Adobe Air/Flex apps to be compiled into a native iOS app, the effect this has on performance is often noticeable, and I've yet to see a notable studio develop anything significant using that technology (not mature enough at this point).
As a quick tip, any game that uses GameCenter HAS to use Objective-C.
the iPhone apps you can download from the appstore are made in Objective-C. For the Android platform, the main language for creating apps is Java.
Over that, there are frameworks that simplify the programmation and makes it multi-platform(iOS/Android) such as Titanium and others, but i don't have the names in mind.