JTextArea's append () method doesn't seem to work

Question

We were assigned to create a simple compiler as a homework that will take set of instructions (containing variables, conditions, jumps, etc.) and evaluate them. That\'s alre

Answer 1

The code probably is called on the event handling loop, where you cannot have drawing. One would normally use

final String line = bufferedReader.relineadLine();
// final+local var so usable in Runnable.

SwingUtilities.invokeLater(new Runnable() {
    @Override
    public void run() {
        input.append(line + "\n");
    }
} 

Unfortunately it takes some care where to place the invokeLatere (as looping). Better use @AndrewThompson's solution.