I don't get the point in forwarding the console's output in the TextArea or GUI.Instead directly show it in the GUI!
Nevertheless you can use the generated output from some manipulations to print it in the TextArea.
Regarding your first question on output:
Say you want to print a string.
In console you would do, System.out.println("Hello World");
In TextField you would do it as textField.setText("Hello World"); //Depending on the library.
So you can use it as a medium of I/O.
Regarding you second question on input:
Surely you can take input from the user via a text box and get it in the code using
String input = textField.getText(); //Depending on the library.
After getting the input you can compare it with your desired 3 inputs and do the appropriate job.
Tip: It would be a good idea to use Radio Buttons or Check Boxes if there are exactly 3 possible inputs depending on the use. User would prefer a quick operation instead of writing a phrase.