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POwhy does BufferedReader fail to read the final line for an InputStream?
 

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  1. POwhy does BufferedReader fail to read the final line for an InputStream?
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    <p>*Note: To clarify, maybe this question wasn't quite clear on the InputStream being "alive." The connection to the telnet weather service (see below for link) is kept open. The goal is to get <em>all</em> lines coming from the server.*</p> <p>Building from the sample Apache <code>WeatherTelnet</code> <a href="http://svn.apache.org/repos/asf/commons/proper/net/tags/NET_1_0_0/src/java/examples/weatherTelnet.java" rel="nofollow">code</a>, I'm using <a href="http://docs.oracle.com/javase/7/docs/api/java/io/InputStream.html#read%28%29" rel="nofollow">InputStream.read</a> to output the server results (inspired by a <a href="http://www.javamex.com/tutorials/io/character_stream_reader.shtml" rel="nofollow">javamex tutorial</a> idiom) one char at a time, using the <code>chars</code> method:</p> <pre><code>thufir@dur:~$ thufir@dur:~$ java -jar NetBeansProjects/Teln/dist/Teln.jar ------------------------------------------------------------------------------ * Welcome to THE WEATHER UNDERGROUND telnet service! * ------------------------------------------------------------------------------ * * * National Weather Service information provided by Alden Electronics, Inc. * * and updated each minute as reports come in over our data feed. * * * * **Note: If you cannot get past this opening screen, you must use a * * different version of the "telnet" program--some of the ones for IBM * * compatible PC's have a bug that prevents proper connection. * * * * comments: jmasters@wunderground.com * ------------------------------------------------------------------------------ Press Return to continue: ^Cthufir@dur:~$ </code></pre> <p>which is the desired output. However, reading the <code>InputStream</code> with a <code>BufferedReader</code> results in dropping the last line. (Or, at least, it's not printed to the console.) Bad output, using <code>lines</code> method:</p> <pre><code>thufir@dur:~$ thufir@dur:~$ java -jar NetBeansProjects/Teln/dist/Teln.jar ------------------------------------------------------------------------------ * Welcome to THE WEATHER UNDERGROUND telnet service! * ------------------------------------------------------------------------------ * * * National Weather Service information provided by Alden Electronics, Inc. * * and updated each minute as reports come in over our data feed. * * * * **Note: If you cannot get past this opening screen, you must use a * * different version of the "telnet" program--some of the ones for IBM * * compatible PC's have a bug that prevents proper connection. * * * * comments: jmasters@wunderground.com * ------------------------------------------------------------------------------ ^Cthufir@dur:~$ thufir@dur:~$ </code></pre> <p><code>StreamReader</code>code:</p> <pre><code>package teln; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; public class StreamReader { private StreamReader() { } StreamReader(InputStream inputStream) throws IOException { lines(inputStream); } private void chars(InputStream inputStream) throws IOException { do { char ch = (char) inputStream.read(); System.out.print(ch); } while (true); } private void lines(InputStream inputStream) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(inputStream, "UTF-8")); String line = ""; do { System.out.println(line); } while ((line = br.readLine()) != null); System.out.println(line); } } </code></pre> <p>Presumably that last line is "null" somehow? Can the logic be altered so that the final line is printed from within <code>lines</code> just as it is from <code>chars</code>?</p>
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    1. COUm, which line are you referring to? I'm not seeing any difference in your outputs, other than blank lines in the second version... unless you meant the "Press Return to continue" which looks like it may well not be in the input data at all. (Your `chars` method will continue until an exception is thrown, for example...)
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      1. POwhy does BufferedReader fail to read the final line for an InputStream?
      1. USJon Skeet
    2. COreading line by line has this disadvantage, that line has to end with `\n` character, if it does not, it is not considered as a complete line.
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      1. POwhy does BufferedReader fail to read the final line for an InputStream?
      1. USFlash Thunder
    3. CO@JohnKugelman: It would still be returned. I suspect there's something else going on here - unfortunately we don't have enough information about the input data to know what. A short but *complete* program demonstrating the problem would really help.
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      1. POwhy does BufferedReader fail to read the final line for an InputStream?
      1. USJon Skeet
 

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