one.eq(of(2)).cond(of("yes"), of("no"));

The present variant of cond does not supply the original value to the left and right branches. Above, the value is one, but it could be a long composite expression. This is inconvenient. (It also fails to imply that the not-taken branch will not be evaluated, since there is no lambda; this problem is also present in and and or.)

one.condNumber(v -> v.eq(of(2)), v -> of("yes"), v -> of("no"));

This alternative has two problems. First, it is always verbose. Second, because there is no self type, distinct variations must be provided for each type, which makes the name confusing (ifNumber sounds like a typecheck).

If the value must be supplied, switch can be used instead. The only reason to choose the second variant is to enforce evaluation semantics, in which case the parameters of and and or should also be lambdas.