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Java.io Two ways to obtain buffered character stream from unbuffered byte one

I am switching to Java from c++ and now going through some of the documentation on Java IO. So if I want to make buffered character stream from unbuffered byte stream, I can do this in two ways:

Reader input1 = new BufferedReader(new InputStreamReader(new FileInputStream("Xanadu.txt")));

and

Reader input2 = new InputStreamReader(new BufferedInputStream(new FileInputStream("Xanadu.txt")));

So I can make it character and after this buffered or vise versa. What is the difference between them and which is better?

Solution

  • Functionally, there is no difference. The two versions will behave the same way.

    There is a likely to be difference in performance, with the first version likely to be a bit faster than the second version when you read characters from the Reader one at a time.

    • In the first version, an entire buffer full of data will be converted from bytes to chars in a single operation. Then each read() call on the Reader will fetch a character directly from the character buffer.

    • In the second version, each read() call on the Reader performs one or more read() calls on the input stream and converts only those bytes read to a character.

    If I was going to implement this (precise) functionality, I would do it like this:

      Reader input = new BufferedReader(new FileReader("Xanadu.txt"));

    and let FileReader deal with the bytes-to-characters decoding under the hood.

    There is a case for using an InputStreamReader, but only if you need to specify the character set for the bytes-to-characters conversion explicitly.