Questo e il codice puoi aiutarmi ?

codice:
	//JLIST///////////////////////////////////
	
	model = new DefaultListModel<Object>();
	list = new JList<Object>(model);
	list.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
	list.setSelectedIndex(0);
	list.setBounds(20,140,140,100);
	
	    public void actionPerformed(ActionEvent e) {         
	     if(e.getSource() == add) {                        
	        int a = list.getSelectedIndex();
	        indice = new String[10];
	         indice[0] = t2.getText(); 
	         indice[1] = t1.getText(); 
	         indice[2] = t3.getText(); 
	         indice[3] = t4.getText(); 
	         if(a == -1) {                                            
	            a = 0;                                                   
	          } else {
		   a++;
                       }                                                 		     
		 model.addElement(indice[0].toString()); 
		 t1.requestFocus();                              
		 t1.setText(""); t2.setText(""); t3.setText(""); t4.setText(""); 
		 list.setSelectedIndex(a);                            
		 list.ensureIndexIsVisible(a);                       
         }
		  if(e.getSource() == cancella) {
                                int a = list.getSelectedIndex();
		       model.remove(a);
			  
		       int dim = model.getSize();
		        if (a == dim) {
		            a--;
		        }
		          list.setSelectedIndex(a);
		          list.ensureIndexIsVisible(a);