Filbehandling

1
Filbehandling

• Tekstfiler
• Notepad, TextPad
• Word Save As - Tekstfil

2
Pakken java.io.

• klassen File
• File Management

3
Constructor Summary public File(String pathname)

• Creates a new File instance Parameters
• pathname - A pathname string
• Throws
• NullPointerException - If the pathname argument
  is null

4
Metoder

• boolean canRead()
• Tests whether the application can read the file
  denoted by this abstract pathname.
• boolean canWrite()
• Tests whether the application can modify to the
  file denoted by this abstract pathname.

5
Metoder

• Boolean createNewFile()
• Atomically creates a new, empty file named by
  this abstract pathname if and only if a file with
  this name does not yet exist.
• Boolean delete()
• Deletes the file or directory denoted by this
  abstract pathname.

6
Metoder

• boolean exists()
• Tests whether the file denoted by this abstract
  pathname exists.
• boolean isDirectory()
• boolean isFile()  
• String list()
• Returns an array of strings naming the files and
  directories in the directory denoted by this
  abstract pathname.
• static File listRoots()
• List the available filesystem roots.

7
Opprette fil

• import java.io.
• File fnew File("a.txt")
• try
• if (f.createNewFile())
• Skriv_ut("Filen ble laget")
• else
• Skriv_ut("Filen ble ikke laget")
• catch (IOException e)
• Skriv_ut(Feil "e.getMessage())

8
Skrive til fil

•  import java.io.
• File fnew File("a.txt")
• try
• if (f.exists()) return
• FileWriter fmiddlenew FileWriter(f)
• PrintWriter foutnew PrintWriter(fmiddle)
• fout.print("Testing")
  // som System.out.
• fout.println("og ting")
• fout.close()
• catch (IOException e)
• Skriv_ut(Feile.getMessage())

9
Lese fra fil

• File fnew File("a.txt")
• FileReader fmiddlenew FileReader(f)
• BufferedReader innew BufferedReader(fmiddle)
• sin.readLine() // eneste
• in.close()