CODEWITHSUNDEEP
java
BradleyPeh
BradleyPeh

Reputation: 35

I/O Character stream: BufferedReader vs printWriter construction

Why is BufferedReader created as such 

BufferedReader br = new BufferedReader(new InputStreamReader(System.in))

while PrintWriter can be simply constructed like these

 PrintWriter pw = new PrintWriter(System.out, true);

BufferedReader can't be constructed directly from System.in so it requires InputStreamReader to convert bytes to char, is this to make it human readable? But PrintWriter dosen't require a wrap from char back to bytes why is that so, does Java automate it? Because to a machine everything is 1 & 0 anyway.

Upvotes: 0

Views: 195

Answers (2)

Joop Eggen
Joop Eggen

Reputation: 109547

First: - Binary data: byte[], InputStream, OutputStream; - (Unicode) text: String, char, Reader, Writer; - Bridges where binary data has some encoding/Charset and is actually text: InputStreamReader, OutputStreamWriter (converting from/to given or default Charset).

Now consider:

  • System.in is a InputStream.
  • System.out and System.err are a PrintStream extending from OutputStream.

They are conceived as for binary data, which for Unix is quite normal and useful. For a console however not so useful. However PrintStream might be a design mishap/error: it has text support, also for passing a Charset; it is a half OutputStreamWriter.

So see PrintStream as an old unclean class doing what an OutputStreamWriter + BufferedWriter does, however not being a Writer.

BufferedWriter+OutputStreamWriter has the same complexity (though being reversed) as PrintStream. One also sees Scanner: new Scanner(System.in). This is not a Reader, and has superfluous support for tokenizing. It like PrintStream has the advantage of briefness, but is definitely more unclean for its unneeded overhead. (There are quite a lot of bugs mentioned in StackOverflow on Scanner.)

Upvotes: 0

xingbin
xingbin

Reputation: 28279

so it requires InputStreamReader to convert bytes to char, is this to make it human readable?

No, it's for performance. Check this to see the difference between them.

And there are BufferedWriter and BufferedReader, they have similar functions and constructors.

BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bufferedWriter = new BufferedWriter(new PrintWriter(System.out));

Upvotes: 1

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