Create a file in java whish the directory is inside a textfile

Question

I've a textfile called backUp.dat. That file contains a directory path, so I created a simple method to read that file:

public static String readFileAsString(String filename) {
    BufferedReader reader;
    try {
        reader = new BufferedReader(new FileReader(filename));
        String line;
        StringBuilder sb = new StringBuilder();
        while ((line = reader.readLine()) != null) {
            sb.append(line).append("\n");
        }
        reader.close();
        //System.out.println("Current Directory:"+ new File(".").getAbsolutePath());
        return sb.toString();
    } catch (FileNotFoundException ex) {
        Logger.getLogger(Welcome.class.getName()).log(Level.SEVERE, null, ex);
        JOptionPane.showMessageDialog(null, "Il Manque un Fichier de System Contactez Votre Fournisseur","ERREUR",JOptionPane.ERROR_MESSAGE);
        System.exit(0);
    }    catch (IOException ex) {  
        Logger.getLogger(Welcome.class.getName()).log(Level.SEVERE, null, ex);
    }  
    return null;
}

This work perfectly, but here is the problem:

String dir = readFileAsString("backUp.dat");               
File fileEES = new File(dir+"backUp.XML");
if (fileEES.createNewFile()) {
    System.out.println("File is created!");
} else {
    System.out.println("File already exists.");
}

I get this exception:

sept. 08, 2015 10:22:28 PM credittaxiphone.FirstWindow exporterUserInfo
GRAVE: null
java.io.IOException: La syntaxe du nom de fichier, de répertoire ou de volume est incorrecte
    at java.io.WinNTFileSystem.createFileExclusively(Native Method)
    at java.io.File.createNewFile(File.java:1012)
    at credittaxiphone.FirstWindow.exporterUserInfo(FirstWindow.java:565)
    at credittaxiphone.FirstWindow.exit(FirstWindow.java:116)
    at credittaxiphone.FirstWindow.formWindowClosing(FirstWindow.java:413)
    at credittaxiphone.FirstWindow.access$100(FirstWindow.java:42)
    at credittaxiphone.FirstWindow$1.windowClosing(FirstWindow.java:179)
    at java.awt.Window.processWindowEvent(Window.java:2058)
    at javax.swing.JFrame.processWindowEvent(JFrame.java:305)
    at java.awt.Window.processEvent(Window.java:2017)
    at java.awt.Component.dispatchEventImpl(Component.java:4881)
    at java.awt.Container.dispatchEventImpl(Container.java:2292)
    at java.awt.Window.dispatchEventImpl(Window.java:2750)
    at java.awt.Component.dispatchEvent(Component.java:4703)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

On the line:

File fileEES = new File(dir + "backUp.XML");

If I remove dir it works correctly.

The content of backUp.dat is:

D:\\

it will be better with english translate of 3rd line in error message — Sk1X1, Sep 08 '15 at 20:31
I know English isn't your first language, and I respect that. But could you try to make your sentences shorter, and remove all "phrases" that don't contain information (like "hey guys" and "that's all")? "I" in English is written in capital letters, and adding more line breaks would make this infinitely easier to read! Also, the word you're looking for is spelled "which", not "wish", nor "whish". — Marcus Müller, Sep 08 '15 at 20:32

score 2 · Answer 1 · answered Sep 08 '15 at 20:38

Most probably the cause of the filename error is the newline you are appending to each read line in readFileAsString. If you expect backUp.dat to contain just a directory path, you should not append any newlines.

And take care when adding dir and "backUp.XML": A directory separator char (File.separatorChar) might be needed there.

axiopisty · Answer 2 · 2015-09-08T20:51:31.363

If you look at the JavaDocs, you'll see that the File constructor you are trying to use takes a parent directory as the first argument, and a file name as the second argument.

Here is the code you currently have:

String dir=readFileAsString("backUp.dat");               
File fileEES = new File(dir+"backUp.XML");

But the API requires something like this:

File dir = new File(readFileAsString("backUp.dat"));
File fileEES = new File(dir, "backUp.XML");

Please note that these examples do not account for proper exception handling. For a complete reference, see the JavaDoc.

public File(File parent, String child)

Creates a new File instance from a parent abstract pathname and a child pathname string.

If parent is null then the new File instance is created as if by invoking the single-argument File constructor on the given child pathname string.

Otherwise the parent abstract pathname is taken to denote a directory, and the child pathname string is taken to denote either a directory or a file. If the child pathname string is absolute then it is converted into a relative pathname in a system-dependent way. If parent is the empty abstract pathname then the new File instance is created by converting child into an abstract pathname and resolving the result against a system-dependent default directory. Otherwise each pathname string is converted into an abstract pathname and the child abstract pathname is resolved against the parent.

Parameters: parent - The parent abstract pathname child - The child pathname string Throws: NullPointerException - If child is null

Create a file in java whish the directory is inside a textfile

2 Answers2