Constants should not be defined in interfaces

The constant interface pattern is a poor use of interfaces.

That a class uses some constants internally is an implementation detail.

Implementing a constant interface causes this implementation detail to leak into the class's exported API. It is of no consequence to the users of a class that the class implements a constant interface. In fact, it may even confuse them. Worse, it represents a commitment: if in a future release the class is modified so that it no longer needs to use the constants, it still must implement the interface to ensure binary compatibility. If a nonfinal class implements a constant interface,

all of its subclasses will have their namespaces polluted by the constants in the interface.

interface Status {                      // Noncompliant
int OPEN = 1;
int CLOSED = 2;
}

public enum Status {                    // Compliant
OPEN,
CLOSED;
}

public final class Status {             // Compliant
public static final int OPEN = 1;
public static final int CLOSED = 2;
}