package Xwxx;
public class Person {
private String name;
private int age;
public Person() {
}
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}
}
package Xwxx;
public class Student extends Person{
private String name;
private int age;
public Student(){
}
public Student(String name, int age) {
this.name=name;
this.age=age;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + "]";
}
}
package Xwxx;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class Test {
public static void main(String[] args) {
ArrayList<Person> list=new ArrayList<Person>();
list.add(new Person("zhangsan",28));
list.add(new Person("lisi",18));
printCollection(list);
ArrayList<Student> l=new ArrayList<Student>();
l.add(new Student("小明",22));
l.add(new Student("小红",20));
printCollection(l);
}
public static void printCollection(Collection<?> list){
//变成了object类了，所以只能访问object的方法
//？ extends Person是接收Person和其子类
//？ super Student是接收Student和其父类
Iterator<?> it=list.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
}
}
原文：https://www.cnblogs.com/hankai2735/p/9105782.html