public class ClassCastTest { public static void main(String[] args) { FiClass fiClass=new FiClass(); BaseClass baseClass=new BaseClass(); BaseClass baseFi=new FiClass();//向上转型不需要强转 BaseClass f2=(BaseClass)new FiClass(); // FiClass fiBase=(FiClass) new BaseClass();//会有异常，因为父类不能直接强转为子类 FiClass ff=(FiClass) baseFi;//没有异常，因为当该引用类型的引用是父类但是对象是子类（已经经过向上转型）,可以进行强转 System.out.println(fiClass instanceof FiClass); System.out.println(baseClass instanceof BaseClass); System.out.println(baseClass instanceof FiClass); System.out.println(fiClass instanceof BaseClass); System.out.println(ff instanceof BaseClass); System.out.println(ff instanceof FiClass); } } class BaseClass{ private int num; public void setNum(int num) { this.num = num; } public int getNum() { return num; } } class FiClass extends BaseClass{ private String f; public void setF(String f) { this.f = f; } public String getF() { return f; } }