I have a friend, he've grown a citrus plant for the last 3 years in a half barrel container and now its 6 feet tall but haven't produce any fruit yet. my question is what kind of citrus can it possibly be (I ask him and he doesn't know) and how can it get that big in 3 years mean while I have a Calamondin tree that is 3 years old,, 1.5 foot tall and start to produce fruit already. Thank you in advance.

Vince

Was your friend's plant started from a seed or from a cutting? Is your friends plant growing indoors or outside? And yours? Could you please ask your friend to take some detailed photos of the plant.
Knowing the location of your plant and your friend's plant will help also.

Many citrus types are fast growers but do not set fruit until many years old. Your Calamondin is a dwarf variety of citrus. Are you judging age by when you received the plant, when you rooted a cutting, or when a seed sprouted? Without knowing the origin, it is hard to know what to expect.

Yes, and I agree with greene that we'd need to see pictures. But even that might not tell us a lot about which citrus it is. Unless it's a grapefruit, which tend to have larger leaves with a lobe at the stem end, most citrus look very much alike.

He may have to wait until it produces a fruit to know.

Your Calamondin is a much better type of citrus for growing in a container. It will stay smaller its whole life. The biggest Calamondin tree I've seen here is about 12ft. tall and 8ft wide. Very beautiful and productive.