ash-java/src/main/java/org/eiichiro/ash/Shell.java
public void register(Command command) {
		Preconditions.checkArgument(command != null, "Parameter 'command' must not be [" + command + "]");
		register(command.name(), command);
	}
public void register(Command command) {
		Preconditions.checkArgument(command != null, "Parameter 'command' must not be [" + command + "]");
		register(command.name(), command);
	}
Registers the specified command instance into the shell.

@param command Command to be registered.