title: Showing text in JTextArea while calculating
body: <p>An application I am writing consists, among others, a JButton and a JTextArea. A click on the button leads to a long calculation, resulting in a text shown in the JTextArea. Even though the calculation is long, I can have middle-results on the go (think, for example, of an application which approximates pi up to 100 digits - every few seconds I could write another digit). The problem is, that even if I write (being in the ActionListener class because the button invoked the calculation) to set the text of the JTextArea to something, it isn't shown while the calculation is done, and I can only see the end result, after the calculation is over.</p>
  
  <p>Why is it so, and how can I fix it?</p>
  
  <p>Thank you in advance.</p>