What can be stated about the variables in an interface?

In an interface, all variables declared are implicitly public, static, and final. This means that any variable in an interface cannot be private or non-final, as they must adhere to certain access and modifier rules. The public modifier allows the variables to be accessible from any class that implements the interface, while the static modifier signifies that the variable belongs to the interface itself rather than any object instance. The final modifier mandates that the variable must be assigned a value exactly once—typically at the time of declaration—and cannot be changed afterward.

The options regarding non-final or non-static variables, initialization within the implementation, and the requirement to be static only are not aligned with the rules governing interfaces in Java, which clearly outline that interface variables contradict these possibilities. Thus, the statement that they are public by default and cannot be private aptly summarizes the nature and restrictions of variables in an interface.