Using replace with DocumentListener

Question

I have two textareas. When I type something in the first textarea, it shows up in the second one with documentlistener. I want to use replace to replace certain words with different words (like a translator).

My DocumentListener looks like this:

DocumentListener documentListener = new DocumentListener() {

    public void changedUpdate(DocumentEvent documentEvent) {
        printIt(documentEvent);
    }
    public void insertUpdate(DocumentEvent documentEvent) {
        printIt(documentEvent);
    }
    public void removeUpdate(DocumentEvent documentEvent) {
        printIt(documentEvent);
    }
    private void printIt(DocumentEvent documentEvent) {
        DocumentEvent.EventType type = documentEvent.getType();
        String typeString = null;
        if (type.equals(DocumentEvent.EventType.CHANGE)) {
        }  
        else if (type.equals(DocumentEvent.EventType.INSERT)) {
            String hello = area1.getText();
        hello.replace("hei", "hello");
        area2.setText(hello);
        }
        else if (type.equals(DocumentEvent.EventType.REMOVE)) {
            String hello = area1.getText();
        area2.setText(hello);
        }
    }
};

This doesn't work though. I thought the hello.replace would replace the word hei typed in area1 with hello, which would be displayed in area2. However, it doesnt change the word. So what am I doing wrong?

Thanks!

Answer 1

Strings are immutable; they can't be changed. And so:

hello.replace("hei", "hello");

Should be:

hello = hello.replace("hei", "hello");

Replace method has to return you a NEW string with your changes in it because it can't modify the original.