Thread: Timer inside loop

Hello. On button click, I have some loop and inside it I want to append jTextArea with some data. I want to do it for example every 3 seconds. For example:
answer1 printed 11:13:10
answer1 printed 11:13:13
answer3 printed 11:13:16
answer4 printed 11:13:19

and so on.

private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        if (kiek > 0 && jTextArea1.getLineCount() > 0) {
            String str;
 
            BufferedReader reader = new BufferedReader(
                    new StringReader(jTextArea1.getText()));
            double prog = 0;
            try {
                while ((str = reader.readLine()) != null) {
 
                    if (str.length() > 0) {
                        jTextArea2.append("---------------------\n");
 
                        jTextArea2.append("Working with IP " + str + "\n");
                        for (int j = 0; j < a.size(); j++) {
 
                            jTextArea2.append(a.get(j) + "\n");
                        }
                    }
                    prog += (double) 100 / (double) jTextArea1.getLineCount();
                    jProgressBar1.setValue((int) (prog));
                }
 
            } catch (IOException ex) {
            }
        }
 
    }

I get each line of other TextArea, print it to current, and also add some information from ArrayList a jTextArea2.append(a.get(j) + "\n");

All I want is that every output to textarea would be periodical for example for 3 seconds.
I tried to do it with Thread.pause(); but in that way, it is waiting for all function to end, and then outputs all data in one time.