java://Comparator、Comparable的用法(按照要求将map集合的键值对进行顺序输出)

import java.util.*;

public class Person implements Comparable<Person>//使Person的属性具有比较性

{

PRivate String name;

private int age;

public Person(String name,int age)//初始化构造函数

{

this.name = name;

this.age = age;

}

public void set(String name,int age)//重新设置姓名和年龄

{

this.name = name;

this.age = age;

}

public String getName()//获取姓名

{

return name;

}

public int getAge()//获取年龄

{

return age;

}

public String toString()//将姓名和年龄以字符串的形式返回

{

returnname+","+age;

}

//出现重名时,再找到另一个hash地址用来存储数据(底层自动调用)

publicinthashCode()

{

returnname.hashCode()+age*34;

}

//判断接受的类是不是Person类,不是就抛出异常(底层自动调用)

publicbooleanequals(Object obj)

{

if(!(objinstanceofPerson))

thrownew ClassCastException("不是Person类");

Person p = (Person)obj;

returnthis.name.equals(p.name) &&this.age==p.age;

}

public int compareTo(Person p)//(按照自己的要求去作比较)

{

int num=new Integer(this.age).compareTo(p.age);

return num==0?this.name.compareTo(p.name):num;

}

}

public class Test

{

public static <T>void sop(T t)

{

System.out.println(t);

}

public static void main(String args[]) throws Exception

{

//创建一个map集合,用来存储数据 <>表示接收的是泛型,即指定的类型

TreeMap<Person,String> map = new TreeMap<Person,String>(/*new Mycompare()*/);

//往集合添加数据

map.put(new Person("czhangsan1",11),"beijing");

map.put(newPerson("zhangsan5",15),"nanjing");

map.put(newPerson("azhangsan5",10),"shanghai");

map.put(newPerson("zhangsan2",20),"haierbing");

map.put(newPerson("bzhangsan2",20),"beijing");

map.put(newPerson("zhangsan3",12),"shanghai");

map.put(newPerson("zhangsan4",19),"changchun");

map.put(newPerson("zhangsan4",10),"changchun");

map.put(new Person("zhangsan4",10),"zhengzhou");

//将map集合转换为set集合,因为map集合没有迭代器 ，而set集合有

Set<Map.Entry<Person,String>> entryset = map.entrySet();

//获取迭代器

Iterator<Map.Entry<Person,String>> it = entryset.iterator();

//用迭代器取数据

while(it.hasNext())

{

Map.Entry<Person,String> m = it.next();

Person key = m.getKey();//取出键

String value =m.getValue();//取出值

sop(key+"......."+"adress:"+value);//打印键和值

}

}

}

class Mycompare implements comparator<Perosn>//自定义一个比较器

{

public int compare(Person p1,Person p2)

{

int num = p1.getName().compareTo(p2.getName());

return num==0?new Integer(p1.getAge()).compareTo(new Integer(p2.getAge())):num;

}

}

//注意：上面的两种形式都实现了比较,任选其中一种就可以。要么实现comparable接口；要么在集合中传入自定义的比较器。