How to solve failure to close a FileStream

Question

I have closed file steam in try/finally, but code analysis warns me:

• Possible failure to close a FileOutputStream
• Possible failure to close a PrintWriter
• Possible failure to close an OutputStreamWriter

How can failure happen? How can I ensure the FileStream is closed?

public void writeFile(String filepath)
{
    BufferedWriter bw = null;
    PrintWriter pw = null;
    try {
        File file = new File(filepath);
        bfw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF-8"));
        pw = new PrintWriter(bfw);

     //do something

    }catch(Exception e){
        e.printStackTrace();
    }
    finally{
        try{
            bfw.close();
            pw.close();
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

Answer 1

How can failure happen?

See your finally block:

finally{
    try{
        bfw.close();   <== exception occured here
        pw.close();    <== this is not execute
    }catch(Exception e){
        e.printStackTrace();
    }
}

What if an exception occurs in bfw.close()? pw.close() will never execute. And this leads to a resource leak.

How can I ensure the FileStream is closed?

Someone already pointed out using try/catch/finally inside finally. But if you don't like to see so many try catch finally I would suggest you to use a library like Apache Commons IO.

Solution:

try {

   ........
} finally {
    IOUtils.closeQuietly(bfw);
    IOUtils.closeQuietly(pw);
}

And yes, you always have try-with-resources if using Java 7 or above.