Interface methods are declared using interface-method-declarations:

interface-method-declaration

attributes_optnew _opt return-type identifier ( formal-parameter-list_opt ) ;

The attributes, return-type, identifier, and formal-parameter-list of an interface method declaration have the same meaning as those of a method declaration in a class (17.5). An interface method declaration is not permitted to specify a method body, and the declaration therefore always ends with a semicolon.