direct System.out to file AND console

[Sebastian Janisch]

hello,

i was wondering what is the best way to direct all calls on system.out to a file, but still also show the output in the console ...

i came up with the following code, but it looks somehow cumbersome, since you would have to overwrite all implemented mehtods

 
class MultiPrintStream extends PrintStream {
    private PrintStream[] streams;

    public MultiPrintStream (PrintStream... streams} {
        /*
         * make the compiler shut up
         */
        super(streams[0]);

        this.streams = streams;
    }

    public void println(String s) {
        for(PrintStream ps : this.streams)
            ps.println(s);
    }

    /*
     * overwrite all other methods
     */
}

 

the implementing code would look like this

public class Test {
    
    static {
        System.out = new MultiPrintStream (System.out, new PrintStream (new File("/home/user/out.txt"));
    }

}
    

is there a better way to achieve this ?

[Henry Wong]

i came up with the following code, but it looks somehow cumbersome, since you would have to overwrite all implemented mehtods

Yea, printstream has a lot of methods... it may be better to write a multi output stream that overrides filter output stream.

Keep in mind that system out is, by default, just a printstream around a file output stream with the STDOUT file descriptor. So, instead of a multi printstream that contains the original printstream and another print stream around a file output stream, a better option would be a print stream around a multi output stream that contains the file output stream of stdout and file output stream of the file.

Something like this...

 
   printstream ---> multioutputstream  --> fileoutputstream (STDOUT)
                                        --> fileoutputstream (file)
   

Only 5 methods to override...

Henry

[Sebastian Janisch]

hey,

i hope i got that right ...
the general idea of the implementation is correct but instead of overriding PrintStream I override FilterOutputStream to have less methods to overwrite ?

[Henry Wong]

Sebastian Janisch wrote:hey,

i hope i got that right ...
the general idea of the implementation is correct but instead of overriding PrintStream I override FilterOutputStream to have less methods to overwrite ?

Yup... And BTW, you can't assign to the System.out variable -- it is final and can't be reassigned. You have to use the setOut() method instead (to reassign the variable).

Henry

[Sebastian Janisch]

true, i forgot about that part ...

okay cool thank you