How To Write Stuff Into Text Files

I'm refitting a snippet of code I found on the net to write stuff into text files. After a bit of fiddling, here's what the code looks like in one of my classes:

public void addItem(String Item){
try{
Writer out = new OutputStreamWriter(fos, "UTF8");
out.append(Item);
out.flush();
// out.close();
}
catch (IOException e) {
System.out.println(e.toString());
}
}

The original snippet included the close() method. However, when I tried to do a test run writing multiple lines, I'd get an IOException about the stream being closed. I removed the close() method line, everything seems to work the way I want it, but I just wanna know if there's anything I'm missing out on by not having the close() method anywhere, especially when the IDE finds it important enough that it lit a warning about the stream not being closed somewhere as I was repurposing the original snippet.