阅读下列代码片段
class InterestTest________ActionListener{
public void actionPerformed (ActionEvent event) {
double interest = balance * rate/100;
balance += interest;
number Format format =Number Format.getCurrencyInstance ();
System.out.printlb{"balance = "+Formatter.format (balance)};
}
private double rate;
}
在下划线处，应填的正确选项是：