This section of the JLS lists all the possible interace modifiers:
�9.1.1 Interface Modifiers InterfaceModifier: one of public protected private abstract static strictfp The access modifier public is discussed in �6.6. Not all modifiers are applicable to all kinds of interface declarations. The access modifiers protected and private pertain only to member interfaces within a directly enclosing class declaration (�8.5) and are discussed in �8.5.1. The access modifier static pertains only to member interfaces (�8.5, �9.5). A compile-time error occurs if the same modifier appears more than once in an interface declaration.