将List <BaseClass>复制到List <DerivedClass>

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<BaseClass> baseList = new ArrayList<>();
        List<DerivedClass> derivedList = new ArrayList<>();

        // 添加元素到 baseList 中
        baseList.add(new BaseClass());
        baseList.add(new DerivedClass());

        // 将 baseList 复制到 derivedList 中
        for (BaseClass base : baseList) {
            if (base instanceof DerivedClass) {
                derivedList.add((DerivedClass) base);
            }
        }

        // 输出 derivedList 的大小
        System.out.println(derivedList.size());
    }
}

class BaseClass {
}

class DerivedClass extends BaseClass {
}