java.java

package com.data;

public interface Animal {

    public String getName();
}

/**/

class Cat implements Animal {

    private String name;

    public Cat() {
    }

    public Cat(String name) {
        this.name = name;
    }

    @Override
    public String getName() {
        return name;
    }
}

/**/
public class Dog implements Animal {
    private String name;
    private Integer age;

    public Dog() {}

    public Dog(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String getName() {
        return null;
    }
}

/* 重点这里 */

public class AnimalInfo<T extends Animal> {

    private final T animal;

    public AnimalInfo(T animal) {
        this.animal = animal;
    }

    public Set<String> process() {
        return Arrays.stream(this.animal.getClass().getDeclaredFields()).map(Field::getName).collect(Collectors.toSet());
    }
}

/**/

public class Main {
    public static void main(String[] args) {
        AnimalInfo<Cat> catInfo = new AnimalInfo<>(new Cat("tom"));
        Set<String> catFields = catInfo.process();
        System.out.println(catFields);

        AnimalInfo<Dog> dogInfo = new AnimalInfo<>(new Dog("jim", 8));
        Set<String> dogFields = dogInfo.process();
        System.out.println(dogFields);
    }
}

/*打印结果*/
// [name]
// [name, age]