Sample/Demo Apps

I am new to app development but learn many other tool previously,

What i found that in other tool like i learn VB6 i can google and get many many samples project done that we can use and learn how people code and then even some we can use free to edit it as per our own.

Is there any site or link where we can get sample project , just open those and learn those and if they allow we can even modify them.

Hope you get my questioon