Java类的泛型参数能作为另外一个泛型类的参数传入吗？

Question

最近遇到一个棘手的泛型问题，精简化后，代码如下：

 import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;


public class testMain {
    public static void main(String[] args) throws IllegalAccessException, InstantiationException {
        People people = new People();

        people.doIt("I'm a student!");
    }
}

interface Say {
    void say(String word);
}

class Student implements Say {
    public void print(String say) {
        System.out.println(say);
    }

    @Override
    public void say(String word) {
        print(word);
    }
}

interface ExecutorCallbackHandler<M, P> {
    void execute(M mapper, P param);
}


class DoSomeThing {

    public <M, P> void batchDo(ExecutorCallbackHandler<M, P> executorCallbackHandler, P param) throws IllegalAccessException, InstantiationException {
        Type[] genTypes = executorCallbackHandler.getClass().getGenericInterfaces();
        Type[] params = ((ParameterizedType) genTypes[0]).getActualTypeArguments();
        Class<M> mapperClass = (Class<M>) params[0];
        M mapper = mapperClass.newInstance();
        executorCallbackHandler.execute(mapper, param);
    }
}

class AbstractPeople<M extends Say> {

    private DoSomeThing doSomeThing = new DoSomeThing();

    public void doIt(String param) throws InstantiationException, IllegalAccessException {
        doSomeThing.batchDo(new ExecutorCallbackHandler<M, String>() {
            @Override
            public void execute(M people, String param) {
                people.say(param);
            }
        }, param);
    }
}

class People extends AbstractPeople<Student> {
}

泛型参数Student，经过AbstractPeople.doIt传入DoSomeThing.batchDo，但是解析时，泛型参数M并未解析成Student，导致出现异常。

请问，是什么原因，如何解决

Answer 1

调试时，参数M并未按预期转换成Student类型