14.3类型转换前先做检查

instanceof：是RTTI的第三种方式，用来告诉我们对象是不是某个特定类型的实例,使用时只可将其与命名类型去比较，而不能与Class对象去比较。

package com.package14;
import com.zx.chapter11.pets.Dog;
import com.zx.chapter11.pets.Pet;
import com.zx.chapter11.pets.Pug;
public class InstanceofDemo01 {
    public static void main(String[] args) {
        Pet pet = new Pet();
        Dog dog = new Dog();
        Pug pug = new Pug();
       if (pug instanceof Pet){
           System.out.println("pug是pet的一个实例");
       }
        if (dog instanceof Pet){
            System.out.println("dog是pet的一个实例");
        }
    }
}

动态的instanceOf：

比instanod的扩展性高

package com.package14;
import com.zx.chapter11.pets.Dog;
import com.zx.chapter11.pets.Pet;
import com.zx.chapter11.pets.Pug;
public class InstanceofDemo02 {
    public static void main(String[] args) {
        Pet pet = new Pet();
        Dog dog = new Dog();
        Pug pug = new Pug();
        test(dog);
        test(pug);
    }
    static void test(Pet p){
        Class<Pet> petClass = Pet.class;
        if (petClass.isInstance(p)){
            System.out.println(p+"是pet的一个实例");
        }
    }
}

应用：

public interface Fari {//通过接口做一个判断，看是否实现了接口
}

package com.package14;
public abstract class Seller implements Fari {//实现了接口，则所以的子类也实现了Fari接口
  public void sell(){};
}
class SuperMakeretSeller extends Seller{
    @Override
    public void sell() {
        System.out.println("到实体店买东西");
    }
}
class ElentcSeller extends Seller{
    @Override
    public void sell() {
        System.out.println("网上购物");
    }
}

package com.package14;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class SellerApp {
    static void test(Fari fari) throws Exception {
        Class<? extends Seller> sellerClass = Seller.class;
        if (sellerClass.isInstance(fari)){
            Method sell = sellerClass.getMethod("sell");
            sell.invoke(fari);
            System.out.println("做活动");
        }
    }
    public static void main(String[] args) throws Exception {
        ElentcSeller elentcSeller = new ElentcSeller();
        test(elentcSeller);
    }
}