学步园

import java.util.*;

class People{
 private String name;
 public People(String name){
  this.name=name;
 }
 public String getName(){return name;}
 public String toString(){return name;}
}

class Pet{
 String name;
 public String getName(){return name;}
 public String toString(){return name;}
}

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

}

class Dog extends Pet{
 public Dog(String name){
  this.name=name;
 }
} 

class Pig extends Pet{
 public Pig(String name){
  this.name=name;
 }
} 

public class MapOfList{
 public static void main(String[] args){
  Map<People,List<? extends Pet>> petPeople=new HashMap<People,List<? extends Pet>>();
  petPeople.put(new People("zhangsan"),Arrays.asList(
                new Cat("cat_zhangsi"),
                new Dog("dog_zhangsan")
                )
       );
  petPeople.put(new People("lisi"),Arrays.asList(
                new Cat("cat_lisi"),
                new Pig("pig_lisi")
                )
       );
  petPeople.put(new People("wangwu"),Arrays.asList(
                new Cat("cat_wangwu"),
                new Dog("dog_wangwu"),
                new Pig("pig_wnagwu")
                )
       ); 
      
     System.out.println(petPeople);
    
     for(People p:petPeople.keySet()){
      System.out.println(p+" has :");
      for(Pet k:petPeople.get(p))
      System.out.print(k+" , ");
      System.out.println();
     }
 }
}