de.frame4j.io

Interface FileVisitor

All Known Implementing Classes:

Del, Era, FileVisitor.Ask, FileVisitor.AskConsImpl, FileVisitor.AskGrafImpl, SVNkeys, SVNkeys.MyTask

@MinDoc(copyright="Copyright  2001 - 2002, 2009  A. Weinert",
        author="Albrecht Weinert",
        version="V.33",
        lastModified="27.03.2021",
        usage="use implementing classes to act on directories and files",
        purpose="a visitor for files and directories")
public interface FileVisitor

A Visitor for files and directories.

An object of an implementing class realises an action on (exactly) one file or directory implemented as the method visit(File). This method is the concrete action and may be whatever the application has to to — delete, list, ask an controller / observer what to do or else.

This interface is implemented by embedded classes here, FileVisitor.Ask, FileVisitor.AskConsImpl, FileVisitor.AskGrafImpl) and in the class FileService. Via FileService it is used in most Frame4J's file handling tools.


© Copyright 2000 - 2003, 2004 Albrecht Weinert

See Also:

FileService, FileCriteria, FileService.doUpdate(java.io.File, java.io.File, java.io.File, java.io.PrintWriter)

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	FileVisitor.Ask An implementation of FileVisitor: Ask a question on a file.
static class	FileVisitor.AskConsImpl An implementation of FileVisitor (question at console).
static class	FileVisitor.AskGrafImpl An implementation of FileVisitor (question at a window).

Method Summary

Modifier and Type	Method and Description
int	visit(File dD) The "deed" or action with the file visited.

Method Detail

visit

int visit(File dD)

The "deed" or action with the file visited.

This method has to implement the concrete action on a single file or on a single directory. Usually implemented by application classes itself or their inner classes the method will be responsible for getting all application information from there as well as doing all the application's book keeping.

In that sense for actions there is no need for a return value and recommendation for it. The class FileService's working methods dirVisit(.. FileVisitors ..) for example totally ignores those returned values. Nevertheless each implementation must document its return values. See makeInCollectionVisitor(), makeOutputInfoVisitor() and makeOutputListVisitor(), as examples.

Besides this procedural or action aspects classes of this type may alternatively implement a filter or functional aspect (or both). For providing a filter response or function value for the file visited the returned value is what matters. See FileVisitor.AskConsImpl and AskGrafImpl as examples. The return value has to be specified fitting the intended application.

The recommendation for questioning filters — implemented here by AskConsImpl and AskGrafImpl — is:

Return value	Key	Button	Meaning
1	j J y Y	Left	Acknowledge (Answer Ja Yes)
2	o O	-	Acknowledge explicitly for overwriting
3	a A	Middle	Acknowledge explicitly for appending
0	others	Right	Negative, No, Nein
-2	q Q	X Menu	Request to end (Quit)
-1	No answer / reaction within waiting time ( maxWait/10 s).

Parameters:

dD - the file or directory to act upon or to determine a filter / function response about

Returns:

the response; mostly irrelevant under (pure) action / procedural aspects

See Also:

doUpDate()