I have many friends.
I have lots of friends.
I have a large number of friends.
I have loads of friends.
There are many friends of mine.
There are a lot of friends of mine.
There are lots of friends of mine.
I have plenty friends.
之类的吧,就是找a lot of的近义词,能修饰可数名词就行.
顺便说一句,mate的意思是"伙伴",如deskmate(同桌),但不一定是朋友.