Writing to txt file from StringWriter

I have a StringWriter variable, sw, which is populated by a FreeMarker template. Once I have populated the sw, how can I print it to a text file?

I have a for loop as follows:

for(2 times)
{
    template.process(data, sw);
    out.println(sw.toString());
}

Right now, I am just outputting to the screen only. How do I do this for a file? I imagine that with each loop, my sw will get changed, but I want the data from each loop appended together in the file.

Edit: I tried the code below. When it runs, it does show that the file.txt has been changed, but when it reloads, the file still has nothing in it.

sw.append("CheckText");
PrintWriter out = new PrintWriter("file.txt");
out.println(sw.toString());