突然地不确定List<Person>集合装入Person对象后还能否添加Perso... - 黑马程序员技术交流社区

/**
* 测试List集合指定Person类型之后是否可以装入子类Employee
* 或者装入Employee对象后是否可以装入父类Person
*/
package day17_Collections;
import java.util.ArrayList;
import java.util.List;
/**
* @author Administrator
*
*/
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
GenericTest1();
}
/*
* 泛型定义Person类型后装入子类Employee测试
*/
public static void GenericTest1() {
List<Person> list = new ArrayList<Person>();
list.add(new Person("郭敬明", 35));
list.add(new Person("張小莉", 28));
list.add(new Person("習大大", 55));
list.add(new Employee("杜海涛", 32, "12345"));
for (Person p : list) {
System.out.println(p);
}
}
/*
* 泛型定义Employee类型后装入子类Person测试
* 无法通过 orz
public static void GenericTest2() {
List<Employee> list = new ArrayList<Employee>();
list.add(new Person("郭敬明", 35));
list.add(new Person("張小莉", 28));
list.add(new Person("習大大", 55));
list.add(new Employee("杜海涛", 32, "12345"));
for (Person p : list) {
System.out.println(p);
}
}
*/
}
class Person {
private String name;
private int age;
Person(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public String toString() {
return this.getClass().getName() + " 姓名:" + name + "|年龄:" + age;
}
}
class Employee extends Person {
private String id;
Employee(String name, int age, String id) {
super(name, age);
this.id = id;
}
public String toString() {
return this.getClass().getName() + " 姓名:" + super.getName() + "|年龄:"
+ super.getAge() + "|学号:" + id;
}
}

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