Domanda Problema di interazione con file di testo.

Luxor_ska · 30 Marzo 2013

Allora ho un problema con questo codice java che sto scrivendo:

Codice:

[LIST=1]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.File[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.FileReader[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.BufferedReader[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.FileWriter[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.BufferedWriter[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.IOException[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]java.io.FileNotFoundException[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]import[/B] [COLOR=#006699]javax.swing.JOptionPane[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*]
[*][COLOR=#000000][B]public[/B] [B]class[/B] Testo [COLOR=#009900]{[/COLOR][/COLOR]
[*]
[*][COLOR=#000000][B]private[/B] [COLOR=#003399]File[/COLOR] f[COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]private[/B] [COLOR=#003399]FileReader[/COLOR] fr[COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]private[/B] [COLOR=#003399]BufferedReader[/COLOR] br[COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]private[/B] [COLOR=#003399]FileWriter[/COLOR] fw[COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]private[/B] [COLOR=#003399]BufferedWriter[/COLOR] bw[COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]public[/B] [COLOR=#003399]String[/COLOR] appoggio[COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][B]public[/B] [COLOR=#003399]String[/COLOR] path[COLOR=#339933];[/COLOR][/COLOR]
[*]
[*][COLOR=#000000][B]public[/B] Testo[COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000] costruttore[COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] leggi[COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] scrivi[COLOR=#009900]([/COLOR]appoggio[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000][COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*][COLOR=#000000][B]public[/B] [COLOR=#000066][B]void[/B][/COLOR] costruttore[COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*]
[*][COLOR=#000000][B]try[/B][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000] [COLOR=#003399]String[/COLOR] path [COLOR=#339933]=[/COLOR] [COLOR=#0000FF]"file.txt"[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] [COLOR=#003399]File[/COLOR] f [COLOR=#339933]=[/COLOR] [B]new[/B] [COLOR=#003399]File[/COLOR][COLOR=#009900]([/COLOR]path[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] [COLOR=#003399]FileReader[/COLOR] fr [COLOR=#339933]=[/COLOR] [B]new[/B] [COLOR=#003399]FileReader[/COLOR][COLOR=#009900]([/COLOR]f[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] [COLOR=#003399]BufferedReader[/COLOR] br [COLOR=#339933]=[/COLOR] [B]new[/B] [COLOR=#003399]BufferedReader[/COLOR][COLOR=#009900]([/COLOR]fr[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] [COLOR=#003399]FileWriter[/COLOR] fw [COLOR=#339933]=[/COLOR] [B]new[/B] [COLOR=#003399]FileWriter[/COLOR][COLOR=#009900]([/COLOR]f,[COLOR=#000066][B]true[/B][/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000] [COLOR=#003399]BufferedWriter[/COLOR] bw [COLOR=#339933]=[/COLOR] [B]new[/B] [COLOR=#003399]BufferedWriter[/COLOR] [COLOR=#009900]([/COLOR]fw[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]  [B]catch[/B] [COLOR=#009900]([/COLOR][COLOR=#003399]FileNotFoundException[/COLOR] path[COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]         [B]try[/B][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]           f.[COLOR=#006633]createNewFile[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000]     [B]catch[/B] [COLOR=#009900]([/COLOR][COLOR=#003399]IOException[/COLOR] e[COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]       e.[COLOR=#006633]printStackTrace[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000]  [COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]  [B]catch[/B] [COLOR=#009900]([/COLOR][COLOR=#003399]IOException[/COLOR] e[COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]      e.[COLOR=#006633]printStackTrace[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000][COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*][COLOR=#000000][B]public[/B] [COLOR=#000066][B]void[/B][/COLOR] leggi[COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]  [COLOR=#003399]String[/COLOR] appoggio[COLOR=#339933];[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]   [B]while[/B][COLOR=#009900]([/COLOR][COLOR=#000066][B]true[/B][/COLOR][COLOR=#009900])[/COLOR] [COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]      [B]try[/B] [COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]            appoggio [COLOR=#339933]=[/COLOR] br.[COLOR=#006633]readLine[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]           [B]if[/B][COLOR=#009900]([/COLOR]appoggio [COLOR=#339933]==[/COLOR] [COLOR=#000066][B]null[/B][/COLOR][COLOR=#009900])[/COLOR][/COLOR]
[*][COLOR=#000000]           [B]break[/B][COLOR=#339933];[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]           [COLOR=#003399]JOptionPane[/COLOR].[COLOR=#006633]showMessageDialog[/COLOR][COLOR=#009900]([/COLOR][COLOR=#000066][B]null[/B][/COLOR],appoggio[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]        [B]catch[/B] [COLOR=#009900]([/COLOR][COLOR=#003399]IOException[/COLOR] e[COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]     e.[COLOR=#006633]printStackTrace[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000]  [COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000][COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*]
[*][COLOR=#000000][B]public[/B] [COLOR=#000066][B]void[/B][/COLOR] scrivi[COLOR=#009900]([/COLOR][COLOR=#003399]String[/COLOR] appoggio[COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]        [COLOR=#003399]JOptionPane[/COLOR].[COLOR=#006633]showInputDialog[/COLOR][COLOR=#009900]([/COLOR]appoggio[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000]        [B]try[/B] [COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]         bw.[COLOR=#006633]write[/COLOR][COLOR=#009900]([/COLOR]appoggio[COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*][COLOR=#000000]         bw.[COLOR=#006633]flush[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000]        [B]catch[/B] [COLOR=#009900]([/COLOR][COLOR=#003399]IOException[/COLOR] e[COLOR=#009900])[/COLOR][COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]     e.[COLOR=#006633]printStackTrace[/COLOR][COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000][COLOR=#009900]}[/COLOR][/COLOR]
[*]
[*][COLOR=#000000] [B]public[/B] [B]static[/B] [COLOR=#000066][B]void[/B][/COLOR] main[COLOR=#009900]([/COLOR][COLOR=#003399]String[/COLOR][COLOR=#009900][[/COLOR][COLOR=#009900]][/COLOR] args[COLOR=#009900])[/COLOR] [COLOR=#009900]{[/COLOR][/COLOR]
[*][COLOR=#000000]     [B]new[/B] Testo[COLOR=#009900]([/COLOR][COLOR=#009900])[/COLOR][COLOR=#339933];[/COLOR][/COLOR]
[*]
[*][COLOR=#000000]    [COLOR=#009900]}[/COLOR][/COLOR]
[*][COLOR=#000000][COLOR=#009900]}[/COLOR][/COLOR]
[/LIST]

In pratica appena può incappa nelle eccezioni...
Es: Se il file non è presente non riesce a generarlo e va nel' eccezione,
quando gli chiedo di leggere va nel' eccezione,
quando gli chiedo di scrivere va nel' eccezione....

L' errore è sempre: Exception in thread "main" java.lang.NullPointerException..
Consigli?

Edit: il codice non si vede neanche D:
http://pastebin.com/k0pNm87a

(scusate se ho sbagliato sezione.)

Jacotsu · 30 Marzo 2013

hai provato a referenziare la classe nel main e poi richiamare i metodi da lì?
PS: è inutile creare un metodo costruttore quando ogni classe ha già il proprio costruttore.

Luxor_ska · 30 Marzo 2013

Scusa ma sono proprio agli inizi... che intendi per referenziare l classe main? (comunque no, non ci ho provato XD).
Per il costruttore... idem per sopra XD
Edit: risolto.

Codice:

import java.io.File;
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.FileWriter;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.FileNotFoundException;
import javax.swing.JOptionPane;


public class Testo {


	private File f;
	private FileReader fr;
	private BufferedReader br;
	private FileWriter fw;
	private BufferedWriter bw;
	public String path;


	public Testo(){
		inizializzatore();
		scrivi();
		leggi();
	}


	public void inizializzatore(){
		try{
			this.path = "file.txt";
			this.f = new File(path);
			this.fr = new FileReader(f);
			this.br = new BufferedReader(fr);
			this.fw = new FileWriter(f,true);
			this.bw = new BufferedWriter (fw);
		}
		catch (IOException e){
			e.printStackTrace();
		}
	}


public void leggi() {
	try {
	   String line;
	   while ((line = br.readLine()) != null) {
	     JOptionPane.showMessageDialog(null, line);
	   }
	}
	catch (IOException ex) {
	     System.err.println("Problemi durante la lettura del file");
	   }
}




	public void scrivi(){
		String appoggio = JOptionPane.showInputDialog("Inserisci la stringa");
		try {
			bw.write(appoggio);
			bw.flush();
			bw.close();
		}


		catch (FileNotFoundException fnfEx){
			try{
				f.createNewFile();
			}
			catch (IOException e){
				e.printStackTrace();
			}
		}
		catch (IOException e){
				e.printStackTrace();
		}
	}




	public static void main(String[] args) {
		new Testo();
	}
}

Jacotsu · 30 Marzo 2013

per referenziare intendo creare un puntatore che si riferisce all'oggetto Testo che hai creato con new.
con che libro lo stai studiando il java?

Domanda Problema di interazione con file di testo.

Luxor_ska

Jacotsu

Luxor_ska

Jacotsu