Accesing a file in the Jar archive

Question

Hello, I am new to Java and I have a problem with my program.
I am writing an application that among other things can read text files.
Every thing works fine as long as run the .class
If I pack the application into a .jar executable (with the text files inside)
I can not reach the files any more.
Probably I am doing something wrong during the packing...
//this is the constructor
public Antenna(File fos){
     try{
     FileReader oos = new FileReader(fos);
     BufferedReader filebuf = new BufferedReader(oos);
                     //I do something with the file
           oos.close();
            } catch (IOException e) {
                                          JOptionPane.showMessageDialog(this,
          "File: " + fos + " NOT FOUND", "Warning",               JOptionPane.ERROR_MESSAGE); }
//I use something like this to initialize my class
Ant1 = new Antenna(new File("Curzola.ant"));When I run my application like .jar (that contains the "Curzola.ant") I get the error unless the file Curzola.ant is external to the jar file in the same directory as the -jar file.
Does someone know what I am getting wrong?
I think it should be easy!!
Thanks
carlo

Answer 1

If you want to read a text file line-by-line, BufferedReader is a good choice.
If you have a InputStream, you can use classes from java.io to convert an
input stream into a BufferedReader:
InputStream -> InputStreamReader -> BufferedReader
For example:
void f(InputStream in) throws IOException {
    Reader r = new InputStreamReader(in, "ISO-8859-1");
    BufferedReader br = new BufferedReader(r);
    //use br
}Some coders would use a different InputStreamReader constructor:
Reader r = new InputStreamReader(in);But that uses the platform's default charset encoding, and since we are
talking about a file in your jar, you shouldn't assume it's being decoded
on the same platform it was encoded.
Your original code, by the way, used FileReader, which is just a convenience
subclass of InputStreamReader, and your code:
FileReader r = new FileReader(file);was just shorthand for
InputStream is = new FileInputStream(file);
Reader r = new InputStreamReader(is);Finally, what objects should your constructor accept? One approach
is to be super flexible and accept many types:
public class Example {
    public Example(URL url) throws IOException {
        this(url.openStream());
    public Example(File file) throws IOException {
       this(new FileInputStream(file));
    public Example(InputStream in) throws IOException {
        this(new InputStreamReader(in, "ISO-8859-1"));
    public Example(Reader r) throws IOException {
        BufferedReader br = new BufferedReader(r);
        //use br
}The other extreme is to accept one basic type. In your case, since you want to read text, is to accept a Reader:
public class Example {
    public Example(Reader r) throws IOException {
        BufferedReader br = new BufferedReader(r);
        //use br
}...and have the calling code do the work of constructing an appropriate reader.