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POHow do I handle multiple streams in Java?
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copied!<p>I'm trying to run a process and do stuff with its input, output and error streams. The obvious way to do this is to use something like <code>select()</code>, but the only thing I can find in Java that does that is <code>Selector.select()</code>, which takes a <code>Channel</code>. It doesn't appear to be possible to get a <code>Channel</code> from an <code>InputStream</code> or <code>OutputStream</code> (<code>FileStream</code> has a <code>getChannel()</code> method but that doesn't help here)</p> <p>So, instead I wrote some code to poll all the streams:</p> <pre><code>while( !out_eof || !err_eof ) { while( out_str.available() ) { if( (bytes = out_str.read(buf)) != -1 ) { // Do something with output stream } else out_eof = true; } while( err_str.available() ) { if( (bytes = err_str.read(buf)) != -1 ) { // Do something with error stream } else err_eof = true; } sleep(100); } </code></pre> <p>which works, except that it never terminates. When one of the streams reaches end of file, <code>available()</code> returns zero so <code>read()</code> isn't called and we never get the -1 return that would indicate EOF.</p> <p>One solution would be a non-blocking way to detect EOF. I can't see one in the docs anywhere. Alternatively is there a better way of doing what I want to do?</p> <p>I see this question here: <a href="https://stackoverflow.com/questions/60302/starting-a-process-with-inherited-stdinstdoutstderr-in-java-6#60578" title="Processes with inherited stdin/stdout/stderr in Java">link text</a> and although it doesn't exactly do what I want, I can probably use that idea, of spawning separate threads for each stream, for the particular problem I have now. But surely that isn't the only way to do it? Surely there must be a way to read from multiple streams without using a thread for each?</p>

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