PrintWriter and FileWriter Instead of using File or Using File ( JAVA ) Program

Question

For the simplicity of writing a lot and also boring you guys I just have a question and if you guys can give me another example as well using maybe something simpler.

Here is the code

PrinterWriter w = new PrinterWriter(new FileWriter("test.txt"));

ok so the above works perfectly fine but so does this

FileWriter fw = new FileWriter("test.txt");

So does this work

PrintWriter w = PrintWriter(new File("test.text");

Ok so now all of these work but I am more concerned on why does the one in italics work.

I have read some of the documentation and have noticed that it takes a Writer as the constructor argument, which FileWriter is an extension of.

But if that is true then why does this not work (or maybe it does)

FileWriter fw = FileWriter(new PrintWriter("test.txt)); 

I have not yet confirmed if this works but I do not see what this would do anyways ( the others make sense ) but can anyone just explain even the slightest bit of information?

Answer 1

Java uses the Decorator pattern to provide specialized combinations of Writer/Stream

• Writer an object you can write characters to
• PrintWriter specialized Writer that provides formating options, like linebreaks (eg println() ) or `printf`` aso
• OutputStream an object to write bytes to

So:

A FileWriter("test.txt") is an object you can write characters to, that are written to a file.

A PrintWriter(new FilteWriter("test.txt")) is an object that provides formatting options, that writes characters to an object that writes to a file.

A PrintWriter(new File("test.txt")) is semantically the same, a writer with formatting options that writes characters to a file. (just without an extra step)

FileWriter fw = FileWriter(new PrintWriter("test.txt)); does not compile.

Two other common Writers are the BufferedWriter StringWriter . The BufferedWriter o ptimizes for larger chunks of writes, it only writes to the underlying Writer if the buffer is full or flushed. StringWriter is the basic "in memory" implementation that appends to a String.

With that: BufferedWriter( new PrintWriter( new FileWriter("test.txt")));" a chunk based writer with no formatting options, that uses a PrintWriter and FileWriter to write characters to a file.