public static void main(String[] args) throws Exception {
        ArrayList<Integer> list = new ArrayList();
        list.add(6);
        //反射機(jī)制實(shí)現(xiàn)
        Class<? extends ArrayList> clazz = list.getClass();
        Method add = clazz.getDeclaredMethod("add", Object.class);
        add.invoke(list, "歡迎關(guān)注:后端元宇宙");
        System.out.println("list = " + list);
    }

@Data
@AllArgsConstructor
public class Animal {

    /**
     * 動(dòng)物名稱
     */
    private String name;

    /**
     * 動(dòng)物毛色
     */
    private String color;
}

public class Pig  extends  Animal{
    public Pig(String name,String color){
        super(name,color);
    }
}

public class Dog extends Animal {

    public Dog(String name,String color){
        super(name,color);
    }
}

  public static void method(List<? extends Animal> lists){
        //正確 因?yàn)閭魅氲囊欢ㄊ茿nimal的子類
        Animal animal = lists.get(0);
        //正確 當(dāng)然也可以用Object類接收，因?yàn)镺bject是頂層父類
        Object object = lists.get(1);
        //錯(cuò)誤 不能用？接收
        ? t = lists.get(2);
        // 錯(cuò)誤
        lists.add(new Animal());
        //錯(cuò)誤
        lists.add(new Dog());
        //錯(cuò)誤 
        lists.add(object);
        //正確 除了null之外，不允許加入任何元素！
        lists.add(null);
    }

 public static void method(List<? super Dog> lists){
        //錯(cuò)誤 因?yàn)槟悴恢溃康降咨额愋?
        Animal animal = lists.get(0);
        //正確 只能用Object類接收
        Object object = lists.get(1);
        //錯(cuò)誤 不能用？接收
        ? t = lists.get(2);
        //錯(cuò)誤
        lists.add(object);
        //錯(cuò)誤
        lists.add(new Animal());
        //正確
        lists.add(new Dog());
        //正確 可以存放null元素
        lists.add(null);
    }

public class PESC {
    ArrayList<? extends Animal> exdentAnimal;
    ArrayList<? super Animal> superAnimal;
    Dog dog = new Dog("小黑", "黑色");

    private void test() {
        //正確 
        Animal a1 = exdentAnimal.get(0);
        //錯(cuò)誤 
        Animal a2 = superAnimal.get(0);

        //錯(cuò)誤 
        exdentAnimal.add(dog);
        //正確 
        superAnimal.add(dog);
    }
}

 public static <T> void copy(List<? super T> dest, List<? extends T> src) {
        int srcSize = src.size();
        if (srcSize > dest.size())
            throw new IndexOutOfBoundsException("Source does not fit in dest");

        if (srcSize < COPY_THRESHOLD ||
            (src instanceof RandomAccess && dest instanceof RandomAccess)) {
            for (int i=0; i<srcSize; i++)
                dest.set(i, src.get(i));
        } else {
            ListIterator<? super T> di=dest.listIterator();
            ListIterator<? extends T> si=src.listIterator();
            for (int i=0; i<srcSize; i++) {
                di.next();
                di.set(si.next());
            }
        }
    }

public class CollectionsTest {
    
    /**
     * 將源集合數(shù)據(jù)拷貝到目標(biāo)集合
     *
     * @param dest 目標(biāo)集合
     * @param src  源集合
     * @return 目標(biāo)集合
     */
    public static <T> void copy(List<? super T> dest, List<? extends T> src) {
        int srcSize = src.size();
        for (int i = 0; i < srcSize; i++) {
            dest.add(src.get(i));
        }
    }
    
    public static void main(String[] args) {
        ArrayList<Animal> animals = new ArrayList();
        ArrayList<Pig> pigs = new ArrayList();
        pigs.add(new Pig("黑豬", "黑色"));
        pigs.add(new Pig("花豬", "花色"));

        CollectionsTest.copy(animals, pigs);
        System.out.println("dest = " + animals);
    }
    
}

/**
 *  實(shí)體轉(zhuǎn)換工具類
 *  
 *  TODO 說(shuō)明該工具類不能直接用于生產(chǎn)，因?yàn)闉榱舜a看去清爽點(diǎn)，我少了一些必要檢驗(yàn)，所以如果直接拿來(lái)使用可以會(huì)在某些場(chǎng)景下會(huì)報(bào)錯(cuò)。
 */
public class EntityUtil {
  
    /**
     * 集合實(shí)體轉(zhuǎn)換
     *
     * @param target 目標(biāo)實(shí)體類
     * @param list   源集合
     * @return 裝有目標(biāo)實(shí)體的集合
     */
    public static <T> List<T> changeEntityList(Class<T> target, List<?> list) throws Exception {
        if (list == null || list.size() == 0) {
            return null;
        }
        List<T> resultList = new ArrayList<T>();
        //用Object接收
        for (Object obj : list) {
            resultList.add(changeEntityNew(target, obj));
        }
        return resultList;
    }
    /**
     * 實(shí)體轉(zhuǎn)換
     *
     * @param target 目標(biāo)實(shí)體class對(duì)象
     * @param baseTO 源實(shí)體
     * @return 目標(biāo)實(shí)體
     */
    public static <T> T changeEntity(Class<T> target, Object baseTO) throws Exception{
        T obj = target.newInstance();
        if (baseTO == null) {
            return null;
        }
        BeanUtils.copyProperties(baseTO, obj);
        return obj;
    }
}

 private void  changeTest() throws Exception {
        ArrayList<Pig> pigs = new ArrayList();
        pigs.add(new Pig("黑豬", "黑色"));
        pigs.add(new Pig("花豬", "花色"));
        //實(shí)體轉(zhuǎn)換
        List<Animal> animals = EntityUtil.changeEntityList(Animal.class, pigs);
    }

public static <T> List<T> changeEntityListNew(Class<T> target, List<?> list);

public static <T> T changeEntityNew(Class<T> target, Object baseTO)