Re: Exception : java.io.Writer.write(Unknown source)

From:

"Mike Schilling" <mscottschilling@hotmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 3 Dec 2009 13:13:19 -0800

Message-ID:

<hf99lg$d6j$1@news.eternal-september.org>

Daku wrote:

Could some Java guru please help. I am using:
java version "1.6.0_16"
Java(TM) SE Runtime Environment (build 1.6.0_16-b01)
Java HotSpot(TM) Client VM (build 14.2-b01, mixed mode, sharing)

I have a simple command line driven program that outputs large
amounts
of text into a simple text file. In the constructor, I have :
if(filename != null)
{
try
{
outFile = new File(filename);
  if(!outFile.exists())
  {
   outFile.createNewFile();
}
if(outFile != null)
{
   fileWriter = new FileWriter(outFile);
    if(fileWriter != null)
{
            bufferedWriter = new
                          BufferedWriter(fileWriter);
       }
}
}
catch(IOException ioe)
{
System.out.println(" constructor IO exception");
ioe.printStackTrace();
System.exit(0);
}
}

There's no need for all the "if (x !-= null)" checks. "new" never
returns null. Nor is there any reason to create a file so that you
can overwrite it. This can be simplified to

    if (filename !=-null)
    {
        try
        {
            outFile = new File(filename);
            fileWriter = new FileWriter(outFile);
            bufferedWriter = new BufferedWriter(fileWriter);
        }
        catch (IOException ex)
        {
            ...
        }
    }

In the main code body, I have functions that write output to text
file
as:
bufferedWriter.write(<some_text>);

And then I frequently get the IO exception:
java.io.Writer.write(Unknown source)

"unknown source" means simply that the JVM doesn't have a line number
to report. It says nothing about the actual problem being reported.
What's needed to invesitage this is the complete stacktrace, including
the type of exception being throws and the exception message. The
line of code that triggers the exception would be useful too.