怎么让jtextarea一行一行显示！

我现在在写一个swing  gui，要用到线程，具体就是，如何让我创建的线程在jtextarea里一行一行的延迟打印出来！我用了sleep（）方法，但是为什么还是一起出来的  看看部分代码
private void startButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
        final int block=Integer.parseInt(blockTextField.getText());
        final int total=Integer.parseInt(totalTextField.getText());
        if(block>total)
            warnningDialog.setVisible(true);// TODO add your handling code here:
        else
        {
            String str=resultField.getText();        
            String array=str.substring(9);
            char []arr=array.replace(" ", "").toCharArray();//arr[]数组现在存放着访问页面序列
            char []lose=new char[block];
            int flag=0;
            class loseSquence extends Thread
            {
                String sname;
                public loseSquence(String sname)
                {
                    this.sname=sname;
                }
                public void run()
                {                       
                     resultField.append(sname);
                 }             }
            loseSquence []List=new loseSquence[total];
            for(int i=0;i<total;i++)
            {
                List[i]=new loseSquence("\n第"+i+"次淘汰页面序列为");
            }
            for(int i=0;i<total;i++)
            {
                try {
                    List[i].sleep(7000 * i);
                    List[i].start();
                } catch (InterruptedException ex) {
                    Logger.getLogger(Operation.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
         }                 
    }