Reading next line InputStream Java

Question

I have an InputStream that would read from a text file. I noticed that the input stream doesn't read from a blank next line.

Sample text file:

[This is

A test file

Here.]

The code:

while ((str = br.readLine())!= null) {
    System.out.println(str);
}

Some text files would have multiple break lines in between. How do I get the input stream to accept break lines ?

As can be seen from the sample text file, '[This is' is followed by an empty line and then followed subsequently by 'A test file'. How do I read the empty line in between the two sets of strings ? (That is my definition of line break / break line)

What do you mean by a "break line"? You mean a line containing only \r\n or \n (depending on the OS)? — alpian
– alpian, Commented Apr 26, 2011 at 15:15
BufferedReader doesn't skip blank lines--I wonder if what you're seeing as two blank lines could really be CR LF? — Michael Brewer-Davis
– Michael Brewer-Davis, Commented Apr 26, 2011 at 15:19
Yeah, I suggest using a BufferedReader too, I have never had problems with that skipping blank lines. — keepitreall89
– keepitreall89, Commented Apr 26, 2011 at 15:26
InputStream does not have a readLine() method. Could you please post all your code? What are you expecting to read on an empty line? — Ishtar
– Ishtar, Commented Apr 26, 2011 at 15:28
Agreed with @Ishtar: InputStream's deal with bytes not characters -- as such there is no concept of "lines" since there is no concept of characters and as such no concept of '\r' — Liv
– Liv, Commented Apr 26, 2011 at 16:16

Peter Lawrey · Accepted Answer · 2011-04-26 16:14:37Z

3

Do you mean?

while ((str = br.readLine())!= null && str.trim().length()>0) {
    System.out.println(str);
}

This gives you all the non blank lines.

answered Apr 26, 2011 at 16:14

Peter Lawrey

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2 Comments

xmjx Over a year ago

Not super sure here but I'd guess this only gives the first lines until an empty line is read. Plus, it should be !str.trim().isEmpty().

Peter Lawrey Over a year ago

isEmpty() is fine if you have Java 6+.

alpian · Accepted Answer · 2011-04-26 15:28:48Z

1

BufferedReader will read all the lines in the file regardless of whether they're blank or not. It will look for line breaks: LF+CR on Windows and LF on GNU/Linux. According to the BufferedReader documentation:

A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

So, it depends on what your text file really looks like. Does it really have carriage-returns and line-feeds between the lines or is it just displaying that way? You can find this out by looking at the file in a Hex editor (LF is 0x0A and CR is 0x0D). If so, then BufferedReader should be giving you those blank lines.

answered Apr 26, 2011 at 15:28

alpian

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Comments

thotheolh · Accepted Answer · 2011-04-27 01:45:21Z

0

Sorry for the mistake, it's a BufferedReader taking in a InputStream. The BufferedReader did read every line including the next line / break line / line break. The problem was with my algorithm I wrote that simply missed the next line / break line / line break. Sorry for the hassle and trouble.

Thanks for all the answers.

answered Apr 27, 2011 at 1:45

thotheolh

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