List集合对象根据字段排序

//把需要比较的对象实现Comparable接口实现compareTo方法

public class Address implements Comparable<Address> {
String country;
String city;
String name;

public Address(String country, String city, String name) {
super();
this.country = country;
this.city = city;
this.name = name;
}

public String toString(){
return " name:"+this.name+" city:"+this.city+" country:"+this.country;
}

@Override
public int compareTo(Address o) {
　　//如果国家不相等，那么直接比较其他字段
　　if(!this.country.equals(o.country)){
　　　　return this.country.compareTo(o.country);
　　}else if(!this.city.equals(o.city)){
　　　　return this.city.compareTo(o.city);
　　}else{
　　　　return this.name.compareTo(o.name);
　　}
　　}
}

//测试类
public class ComparableTest {
public static void main(String[] args) {
　　List<Address> list = new ArrayList<Address>();
　　Address a1 = new Address("中国", "湖南", "屌丝1");
　　Address a2 = new Address("中国", "湖北", "屌丝2");
　　Address a3 = new Address("美国", "纽约", "屌丝3");
　　Address a4 = new Address("中国", "湖北", "屌丝4");
　　Address a5 = new Address("中国", "湖南", "屌丝5");
　　Address a6 = new Address("中国", "广西", "屌丝6");
　　list.add(a1);
　　list.add(a2);
　　list.add(a3);
　　list.add(a4);
　　list.add(a5);
　　list.add(a6);

　　System.out.println(list);//排序前
　　Collections.sort(list);
　　System.out.println(list);//排序后

　　}
　}
}

//打印结果

[ name:屌丝1 ncity:湖南 ncountry:中国,

name:屌丝2 ncity:湖北 ncountry:中国,

name:屌丝3 ncity:纽约 ncountry:美国,

name:屌丝4 ncity:湖北 ncountry:中国,

name:屌丝5 ncity:湖南 ncountry:中国,

name:屌丝6 ncity:广西 ncountry:中国]

[ name:屌丝6 ncity:广西 ncountry:中国,

name:屌丝2 ncity:湖北 ncountry:中国,

name:屌丝4 ncity:湖北 ncountry:中国,

name:屌丝1 ncity:湖南 ncountry:中国,

name:屌丝5 ncity:湖南 ncountry:中国,

name:屌丝3 ncity:纽约 ncountry:美国]