I've only been 3 months in the company but I'm planning to quit after 2 months starting today ...Should I tell my boss immediately? I'm a fresh grad and this is my first job. I know it might be bad for my resume quitting after 3 months but it's just that I've applied as a Web Developer but they are telling me to learn android and do android development and I think they are wasting resources and time on me that they should've hired an Android Developer.
2 weeks is the standard....
HOWEVER I would strongly advise staying where you are and learning the new technology.
Quitting so quickly after taking a position will make you look lazy, disloyal, and fickle. I would recommend in the strongest terms that you knuckle down, learn the technology and gain the work experience. Quitting so soon after starting is going to burn bridges and give you a bad rep that will haunt you. The business world is a good deal smaller than you think, especially with regards to IT.
More to the point, what happens when you get to the next job and it turns out to be less than rosy? You'll either have to stick it out or have a resume that is going to be very hard to sell to your third employer.
If you give notice now, your company is likely to let you go now, since there is no reason investing anymore in getting you up to speed in a technology, when you are not going to be around to provide returns on their investment.
The company has made it pretty clear that they want and need an android developer and you accepted a position doing this knowing you would have to come up to speed. They have done their part by giving you time to learn the technology. But if you are not going to stick around after you have learned it, they are just throwing their money away trying to teach it to you.
I wouldn't give anymore notice than you are required to.
Check your contract (if you have one). Give them exactly what you are required to. If you do not have a contract, or the contract does not say what the notice period is, give them 2 weeks.
Being this new to the company, you are probably still on probation. That means the company can let you go for any reason. If you tell them you want to leave in 2 months, they may just let you go now so they can hire someone else and get them up to speed.
Also, I wouldn't worry about how it looks on your resume, you have a very reason for that. If some asks why you left, you can tell them exactly what you told us. You were hire as a web developer and they were pushing you to do android development, so you wanted to find a job in web development.