Issue with FileOutputStream in Java

Question

I get a runtime exception when I execute the following code. I cannot see what is wrong.

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintWriter;

public class FileIO {

    public static void main(String[] args){

        File test = new File("test.txt");

        FileOutputStream ostream = new FileOutputStream(test); 

        PrintWriter out = new PrintWriter(ostream);
    }
}

I keep getting a FileNotFoundException. I have tried keeping the file in every possible folder within the project and also tried giving an explicit path, but I keep getting the same exception. Any ideas?

Do you see any difference between compilation time and execution time? — Jagger
– Jagger, Commented Oct 9, 2012 at 22:48
@Jin From which language are you coming from? You should learn about checked and unchecked exceptions in Java. — Jagger
– Jagger, Commented Oct 9, 2012 at 22:50
So...you were getting a compile time error and not a runtime exception? sigh... — pankar
– pankar, Commented Oct 9, 2012 at 22:59

MikeB · Accepted Answer · 2012-10-09 22:44:48Z

2

When I tried this, it didn't even compile. I had to say that the main throws FileNotFoundException

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.io.FileNotFoundException;

public class FileIO 
{

    public static void main(String[] args) throws FileNotFoundException
    {

        File test = new File("test.txt");

        FileOutputStream ostream = new FileOutputStream(test); 

        PrintWriter out = new PrintWriter(ostream);            
    }
}

This worked just fine with no errors

answered Oct 9, 2012 at 22:44

MikeB

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1 Comment

Jin Over a year ago

OK. This works. I hadn't read about throws keyword, so I had no idea.

Bohemian · Accepted Answer · 2012-10-09 22:45:04Z

0

The answer is undoubtedly that the current directory isn't what you think it is.

Add this line of code immediately after initializing the file variable:

System.out.println(test.getAbsolutePath());

The problem should be obvious.

Alternatively, specify an absolute path:

File test = new File("/mydir/test.txt");

answered Oct 9, 2012 at 22:45

Bohemian♦

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1 Comment

Jin Over a year ago

As I said in my post, I had tried giving an explicit path, but it did not work. I had created a text file by this name in every folder in the heirarchy.

pankar · Accepted Answer · 2012-10-09 22:52:25Z

0

Most likely the file test.txt in your current directory is readonly and an attempt to open it for writing (by instantiating a class of type FileOutputStream) is prohibited.

Check the file's permissions or delete it and run your program again (after adding a try catch block for the unhandled FileNotFoundException exception thrown by FileOutputStream.

For instance:

    try {
        ostream = new FileOutputStream(test);
        PrintWriter out = new PrintWriter(ostream); 
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

answered Oct 9, 2012 at 22:52

pankar

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Comments

Geoff Montee · Accepted Answer · 2012-10-09 22:53:36Z

0

Based on File class and FileOutputStream class, try this:

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintWriter;

public class FileIO {

    public static void main(String[] args){

        File test = new File("test.txt");

        if (test.exists()) {
            if (!test.isFile()) {
                System.out.println("File " + test.getAbsolutePath() + " is not a regular file!");
                System.exit(1);
            } else if (!test.canWrite()) {
                System.out.println("Can not write to file " + test.getAbsolutePath() + "!");
                System.exit(1);
            }
        } else {
            test.createNewFile();
        }

        FileOutputStream ostream = new FileOutputStream(test); 

        PrintWriter out = new PrintWriter(ostream);
    }
}

This checks for the common error conditions.

file exists
file isn't a regular file
file cannot be written to

answered Oct 9, 2012 at 22:53

Geoff Montee

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4 Comments

user207421 Over a year ago

new FileOutputStream() already does all those tests, in the kernel, atomically, and provides a message in the exception that says what the problem is if any. Repeating all those tests adds zero value, and it introduces timing-window problems as well. You still have to catch FileNotFoundException: why write all the handling code twice?

Geoff Montee Over a year ago

For a simple reason: The OP didn't know where his code was failing. I offered tests to catch the situations where the exception could have been thrown. I never recommended the above code for production code.

Geoff Montee Over a year ago

Of course, if his code wasn't even compiling, then the file isn't the issue, and none of this matters.

user207421 Over a year ago

The text of the exception would have told him that, if there really had been an exception thrown , which there wasn't.

user207421 · Accepted Answer · 2012-10-10 00:58:26Z

0

I get a runtime exception when I execute the following code.

No you didn't. You got a compiler error message when you tried to compile it. The message told you that new FileOutputStream throws FileNotFoundException and your code doesn't catch it. So fix your code to do that, or have main() declared as 'throws FileNotFoundException'.

answered Oct 10, 2012 at 0:58

user207421

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