javafile-ioconsolefileoutputstreamprintstream

Writing to console and text file


I found the code below from the internet, works but it doesn't write the printed console to omt.txt, it only writes the System.out.println statements after the second catch block.If you run the code once you will understand what I mean.All I want is to write what is on console to the "omt.txt" file that is all...

After some answers, I see that my question wasn't clear, sorry for that. I want to save console output to omt.txt text file. If on the console "Hello 123" is printed , it should be also in omt.txt file.In other words whatever on the console is printed should be simultaneously written on the om.txt file or can be after the console execution but should be 1-to-1 the same!

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;

public class Wrt_file {

    public static void main(String[] args) {
        System.out.println("THIS is what I see on the console. but not on TEXT file"); 

          File f = new File("omt.txt");
          if(!f.exists())
          {
            try {
                       f.createNewFile();
                } catch (Exception e) {
                    e.printStackTrace();
                }
          }

        try {
                FileOutputStream fos = new FileOutputStream(f);
                PrintStream ps = new PrintStream(fos);
                System.setOut(ps);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("THIS is what I see on the text file, but not on CONSOLE");      

        for (int i=0; i<10; i++){

            System.out.println("Testing");  
        }

    }

}

Solution

  • Updated answer after learning that OP wants to duplicate streams

    Since you want to write data in both streams try using TeeOutputStream from Apache Commons. Change your code in second try to

    try {
        FileOutputStream fos = new FileOutputStream(f);
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            try {
                fos.flush();
            }
            catch (Throwable t) {
                // Ignore
            }
        }, "Shutdown hook Thread flushing " + f));
        //we will want to print in standard "System.out" and in "file"
        TeeOutputStream myOut=new TeeOutputStream(System.out, fos);
        PrintStream ps = new PrintStream(myOut, true); //true - auto-flush after println
        System.setOut(ps);
    } catch (Exception e) {
        e.printStackTrace();
    }
    

    Now results from System.out will also be placed in your file.