1：实现Comparable接口

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

class User implements Comparable{

private Integer id;

private String name;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

@Override

public int compareTo(User o) {

if (this.id == o.id) return this.name.compareTo(o.name); //id相同按name排序

else return this.id.compareTo(o.id); //按ID从小到大排序

}

}

public class Main {

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

String s1 = "abx";

String s2 = "小1";

System.out.println(s1.compareTo(s2));

List users = new ArrayList();

User u6 = new User();

u6.setId(6); u6.setName("Jack");

User u = new User();

u.setId(6); u.setName("abx");

User u1 = new User();

u1.setId(1); u1.setName("小1");

User u4 = new User();

u4.setId(4); u4.setName("小4");

User u2 = new User();

u2.setId(2); u2.setName("小2");

User u7 = new User();

u7.setId(6); u7.setName("abc");

users.add(u2);

users.add(u6);

users.add(u4);

users.add(u1);

users.add(u);

users.add(u7);

Collections.sort(users);

for (User ui : users) {

System.out.println(ui.getId() + " " + ui.getName());

}

}

}

2：集合外定义Comparator

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

class User{

private int id;

private String name;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

public class Main {

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

String s1 = "abx";

String s2 = "小1";

System.out.println(s1.compareTo(s2));

List users = new ArrayList();

User u6 = new User();

u6.setId(6); u6.setName("Jack");

User u = new User();

u.setId(6); u.setName("abx");

User u1 = new User();

u1.setId(1); u1.setName("小1");

User u4 = new User();

u4.setId(4); u4.setName("小4");

User u2 = new User();

u2.setId(2); u2.setName("小2");

User u7 = new User();

u7.setId(6); u7.setName("abc");

users.add(u2);

users.add(u6);

users.add(u4);

users.add(u1);

users.add(u);

users.add(u7);

Collections.sort(users, new Comparator() {

@Override

public int compare(User o1, User o2) {

if (o1.getId() == o2.getId()) return o1.getName().compareTo(o2.getName());

return o1.getId() > o2.getId() ? 1 : -1;

}

});

for (User ui : users) {

System.out.println(ui.getId() + " " + ui.getName());

}

}

}