Apply a listener to System.err?

Question

I have this idea, that anytime an unhandled exception occurs in my JavaFX program, that instead of relying on console output, I can display an alert to the user. I am thinking that perhaps I can capture the output from System.err to use. Here is what I have tried thus far.

    PrintStream myStream = new PrintStream(System.err) {
        @Override
        public void println(String s) {
            super.println(s);
            Log.debugLog(s); //this function logs to a file and displays an alert to user
        }
    };
    System.setErr(myStream);

This code segment works if I replace System.err with System.out, and System.setErr to System.setOut . However that is capturing System.out, not System.err. I suppose the better question would be, what exact function does System.err call when displaying an error to the console? So that may override it. Any tips are appreciated.

Answer 1

I think you have the wrong approach. If you want to display an alert to the user when there is an unhandled Exception, you can do that by setting a DefaultUncaughtExceptionHandler:

Thread.setDefaultUncaughtExceptionHandler((t, e) -> {
       // show alert to user
       e.printStackTrace();
       // do whatever you want with the Exception e

    });

Answer 2

You can create a JavaFX Alert customized to show an exception stack trace along with a brief message. This link shows the code for the below.