线上不停机，使用反射动态扩展Java类

可以把newInstance的工厂方法扩展处理，封装到框架中来减少代码的冗余

public class NotReceivingBillUtil {
    private volatile static NotReceivingBillUtil helper = null;
    public static NotReceivingBillUtil newInstance() {
        if (helper == null) {
            synchronized (NotReceivingBillUtil.class) {
                if (helper == null) {
                    String clazzName = NotReceivingBillUtil.class.getName();
                    try {
                        Class clazz = Class.forName(clazzName + "Ex");

                        helper = (NotReceivingBillUtil) clazz.newInstance();
                    } catch (Exception ex) {
                        helper = new NotReceivingBillUtil();
                    }
                }
            }
        }
        return helper;
    }

    protected  void  init(){
        System.out.println("NotReceivingBillUtil类到初始操作");
    }

}

继承原来的类对类的方法进行扩展

public class NotReceivingBillUtilEx extends  NotReceivingBillUtil{

    protected  void  init(){
        System.out.println("Ex扩展类到初始操作");
    }

}

测试调用

 public static void main(String[] args) {
        NotReceivingBillUtil not =NotReceivingBillUtil.newInstance();
        not.init();
 }