Question

I’d like to know how best to make “accessable” or “visible” a set of File I/O Stream constructors defined in my main routine, to sub-routines.

I found that I cannot use “public”, the compiler issues an “Illegal Expression” error msg.

When I place the file I/O stream and channel constructors in the public class defined for
the entire program “package”. The compiler issues an error stating there’s no FileNotFound or IOException handling declared, so I put on my mainline routine the following:

public static void main(String args[]) throws FileNotFoundException, IOException
 { 
     // and if I then place the File I/O contructors after this: 

                   //Connect to the LU62XC Message File 
    FileOutputStream MesgOut = new FileOutputStream(Mesg_File) ;
    FileChannel MesgChnl  =  MesgOut.getChannel() ;
    ByteBuffer  Mesg_Bufr =  ByteBuffer.allocate(128) ; 

           //Connect to the Request Input File 
    FileInputStream RqstInp = new FileInputStream(Rqst_File) ;  
           //Connect to the Response Output File 
    FileOutputStream RespOut = new FileOutputStream(Resp_File) ;
           //Connect to the Request/Response Log File 
    FileOutputStream LogrOut = new FileOutputStream(Logr_File) ;

I resolve the “no exception handling error”, but now my problem is the sub-routines
that reference the “constructed” file objects essentianlly can’t .. I get a bunch of
“symbol not found” error messages. Again, if I put “public” in front of the file I/O constructors, I get the Illegal expression message.

Is there any way out of this ???

Why the java compiler insists on the program handling file-not-found errors is beyond me.
I mean there’s already the if file_object.exists() method…

IF the file’s NOT there.. the OS will let you know. All ANY application program(OOP or otherwise) does when it comes to I/O of any kind is to make a request to the underlying OS.

Answer 1

If you want a method to use an object you have as a local variable you can pass its as an argument. This is standard practice in just about every language I can think of. However instead of passing the FileInputStream it is better to pass the file name in camelCase

// in main
process(requestFile, responseFile, logFile);

// later
public static void process(String requestFile, String responseFile, String logFile) throw IOException {
    //Connect to the Request Input File 
    FileInputStream requestIn = new FileInputStream(requestFile);  
    //Connect to the Response Output File 
    FileOutputStream responseOut = new FileOutputStream(responseFile);
    //Connect to the Request/Response Log File 
    FileOutputStream logOut = new FileOutputStream(logFile);

    requestIn.close();
    responseOut.close();
    logOut.close();
}

I get a bunch of “symbol not found” error messages.

Because a local variable is local to the scope i.e. the method it is in. You can’t use it in another method.

Again, if I put “public” in front of the file I/O constructors, I get the Illegal expression message.

Because public fields cannot be defined in a method, they have to be define outside a method, usually at the start of the class.

Is there any way out of this ???

Reading a few tutorials http://www.google.com/search?q=java+turorials 11 million results, or working example http://www.google.com/search?q=java+examples 25 million results

Why the java compiler insists on the program handling file-not-found errors is beyond me. I mean there’s already the If file_object.exists() method… IF the file’s NOT there..the OS will let you know.

It does let you know by throwing a FileNotFoundException. What do you expect it to do?

All ANY application program(OOP or otherwise) does when it comes to I/O of any kind is to make a request to the underlying OS.

And the OS can return an error which you need to be able to handle.