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<User>{
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<User> users = new ArrayList<User>();
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<User> users = new ArrayList<User>();
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<User>() {
@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());
}
}
}