java如何实现强制类型转换（附代码）

//定义一个父类的对象,可以指向1M内存
People[] staff = new People[2];

//开辟了1.5M内存,但是实际只指向了1M内存
staff[0] = new RichPeople("John", 18, 100,1200);

staff[1] = new RichPeople("Tp",20,200,20000);

//判断staff[0]是否是RichPeople的实例
if(staff[0] instanceof RichPeople){
  RichPeople boss = (RichPeople)staff[0];
  boss.addDeposit(10000);
}