//Use Stringbuilder to add new listbox items 

 private void btnAddNewActionPerformed(java.awt.event.ActionEvent evt)                                          
    {                                              
        // take new item and cost and add to listbox model
      
        String newItem = txtNewItem.getText().trim();
        String newCost = txtNewCost.getText().trim();
                                             
        if (newItem.length() > 0 && newCost.length() > 0)
          {
                StringBuilder myLBItem = new StringBuilder();       //create new string;builder
                myLBItem.setLength(60);                                     //60 chars long to hold new line of data
                myLBItem.insert(0, newItem.toString());                 //new item inserted at column 0
                myLBItem.insert(35, newCost.toString());                //new price inserted at column 35
            
                //---add new item and cost to listbox and sort it
                model.addElement(myLBItem.toString());                  //be sure to convert to string
                sortListBox(model);
                
          }