When to use which Writer subclass in Java; common practices

Question

I have always been slightly confused with the amount of different IO implementations in Java, and now that I am completely stuck in my project development, I was taking my time

Answer 1

PrintWriter doesn't have a constructor that takes an "append" parameter, but FileWriter does. And it seems logical to me that that's where it belongs. PrintWriter doesn't know if you're writing to a file, a socket, the console, a string, etc. What would it mean to "append" on writes to a socket?

So the right way to do what you want is simply:

PrintWriter out=new PrintWriter(new BufferedWriter(new FileWriter(myfile, append)));

Interesting side note: If you wrap an OutputStream in a PrintWriter, Java automatically inserts a BufferedWriter in the middle. But if you wrap a Writer in a PrintWriter, it does not. So nothing is gained by saying:

PrintWriter out=new PrintWriter(new BufferedWriter(new OutputStreamWriter(new FileOutputStream(myfile))));

Just leave off the BufferedWriter and the OutputStreamWriter, you get them for free anyway. I have no idea if there is some good reason for the inconsistency.

It's true that you can't specify a character encoding in a FileWriter as ColinD notes. I don't know that that makes it "unacceptable". I almost always am perfectly happy to accept the default encoding. Maybe if you're using a language other than English this is an issue.

The need to wrap Writers or OutputStreams in layers was confusing to me when I first started using Java. But once you get the hang of it, it's no big deal. You just have to bend your mind into the write framework. Each writer has a function. Think of it like, I want to print to a file, so I need to wrap a FileWriter in a PrintWriter. Or, I want to convert an output stream to a writer, so I need an OutputStreamWriter. Etc.

Or maybe you just get used to the ones you use all the time. Figure it out once and remember how you did it.