Re: how to read back the lines printed out to the console?

From:
=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 30 Jan 2012 19:33:33 -0500
Message-ID:
<4f2736dd$0$291$14726298@news.sunsite.dk>
On 1/30/2012 3:03 PM, frame wrote:

We have an existing Java program, which prints out a lot of message
using System.out.println() method to the console. There are about 500
those calls in the code. We hope to add one more feature: besides
print out to the console as it is doing now, we also want to store
those messages in a text file. So the message will be in two places:
one place -- the console -- is shown the message progressively as the
program is running; another place -- a text file -- is created at the
end of the program.

Since there are about 500 calls in the code, we don't want to add a
duplicated printing method at every printing place. I am thinking to
let the program run as usal, printing out all the messages to the
console, then before the program ends, having a method reading in
every line on the console, which was printed out previously. I just
don't know how to achieve that.


If you can live with the file being written while the
program runs then something like:

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;

public class TeeOutputStream extends OutputStream {
    private OutputStream os1;
    private OutputStream os2;
    public TeeOutputStream(OutputStream os1, OutputStream os2) {
        this.os1 = os1;
        this.os2 = os2;
    }
    public void write(byte[] b) throws IOException {
        os1.write(b);
        os2.write(b);
    }
    public void write(byte[] b, int off, int len) throws IOException {
        os1.write(b, off, len);
        os2.write(b, off, len);
    }
    public void write(int b) throws IOException {
        os1.write(b);
        os2.write(b);
    }
    public void flush() throws IOException {
        os1.flush();
        os2.flush();
    }
    public void close() throws IOException {
        os1.close();
        os2.close();
    }
    public static void test2() {
        System.out.println("This is test2");
    }
    public static void test1() {
        System.out.println("This is test1");
    }
    public static void main(String[] args) throws IOException {
        System.out.println("normal");
        PrintStream sav = System.out;
        System.setOut(new PrintStream(new TeeOutputStream(System.out, new
PrintStream("C:\\work\\tst.out"))));
        test1();
        test2();
        System.setOut(sav);
        System.out.println("normal");
    }
}

Arne

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