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NNTP-Posting-Date: Mon, 30 Jan 2012 21:06:06 -0600
Date: Mon, 30 Jan 2012 19:06:07 -0800
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: how to read back the lines printed out to the console?
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On 1/30/2012 6:49 PM, frame wrote:
> Thank you very much for all the replies. Probably I didn't explain my
> question clear. After reading all the replies, I am sorry I still
> didn't get the idea to proceed.
>
> My problem is such: our finished Java program has many printing
> statements, e.g.
>
> System.out.println("step A: everything is ok");
> ...
> System.out.println("step B: computation starts now");
> ...
>
> if(so)
> {
> System.out.println("warning: temperature is too hot");
> }
>
> There are about 500 of those. When we run the program, all these
> messages show up on the console -- that's good. But now, we also want
> to keep those messages in a file.  I have two ideas, but none of them
> is acceptable:
>
> 1)at the beginning of the program, I added a little piece of code(re-
> direct the System output to a file), now all the existing 500
> System.out.println(..) prints to a file, not the console any more --
> this is not good, because the program runs up to 5 hours, we hope to
> see the message progressively on the console. With this approach, we
> have to wait till the program finished and open the text file to read.

You are almost there. Instead of using a PrintStream subclass that
writes only to the console, or one that writes only to a file, you need
one that writes to both.

Patricia