R- the return type for all command signature methods, usually a new command instance or a command fromFile providing methods for chained invocation of following commands
public interface CommandInterface<R>
Commandcan be invoked (or instantiated). It consists of the different method signatures for the command.
Consider for instance the following simplified
ls command. It can be
called without options, with a file, with option flags or both a file and
options. The command interface for
ls would therefore define four
R ls() R ls(File file) R ls(Ls.Option... options) R ls(File file, Ls.Option... options)Note that all command methods in the interface usually return the generic type
R. Command factories (see
Factoryconstant of a specific command} return a new command instance. Command builders implementing many different command interfaces return an instance to itself (the BUILDER) to allow for method chaining, for instance when creating a joined command.
This interface does not define any methods since all methods are defined by
the concrete command. The interface serves as a marker and documentation
interface. Theoretically, a command interface is not required to extend this
interface, but it is highly recommended. Also, if a command factory is used
GenericCommandBuilder, it must implement this interface.
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