Writing to console and text file

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.

The reason is :

The java.lang.System.setOut() method reassigns the "standard" output stream.

so when you use System.out.println it will print only in the text file

So , if you want to print on the text file and on the console , Try this :

   

    FileOutputStream fos = new FileOutputStream(f);
    PrintStream ps = new PrintStream(fos);
    ps.println("THIS is what I see on the text file, but not on CONSOLE");
    System.out.println("THIS is what I see on the text file, but not on CONSOLE");

        for (int i = 0; i < 4; i++) {

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