阅读下列代码片段：
class InterestTest______ActionListener{
public void actionPerformed(ActionEvent event){
double interest=balance*rate/100;
balance+=interest;
NumberFormat format=NumberFormat.getCurrencyInstance();
System.out.printlb("balance="+Formatter.format.(balance));
}
Private double rate;
}
在下画线处，应填的正确选项是______。