JScrollPane, simple code, why doesnt it work?

Question

i am just learning how to add scroll bars,
i do not understand why my code below doesnt work,
can u tell me how to fix it & what i have done wrong?
appreciated...
// ex 5_17 did not have a large enough display area...
// ex 5_17a changes the way it is displayed, i have added a scroll bar
import javax.swing.JOptionPane;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
public class Ex5_17a{
     public static void main( String args [] ){
          int terms = 1;
          double pie = 4;
          double ans = 0;
          double p = 3;
          JTextArea outputArea = new JTextArea( "15,15");
          JScrollPane scroller = new JScrollPane( outputArea );
          String result = "";
     while (terms < 40){
               terms++;
           if ((terms % 2)==0){
              pie = pie - (double)(4/p);
              ans = pie;}
           else{
              pie = pie + (double)(4/p);
           ans = pie;
           p = p+2;
           result += + pie + "   " + terms + "   " + ans + " \n";
        //outputArea.append(result);
     }//end of while terms<30
     outputArea.setText( result );
        JOptionPane.showMessageDialog(null,
           scroller,"Pie display",JOptionPane.PLAIN_MESSAGE);
     System.exit(0);
     }//end of main
}//end of class
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Answer 1

What does "15, 15" mean?
If you want to initialize ta with number of rows and cols:
JTextArea outputArea = new JTextArea(15, 15);
To make sure you have scrolling that you want one of possibilities of using constants:
scroll = new JScrollPane(ta,
ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);