ArrayList 多关键字排序

ArrayList里面的对象实现 Comparable接口

// User.java 待排序的对象 ，实现了Comparable接口
public class User implements Comparable{

    private String name;
    private String pass;
    private int age;

    public String getName() {
        return name;
    }

    public String getPass() {
        return pass;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setPass(String pass) {
        this.pass = pass;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public int compareTo(Object o) {
        User user = (User) o;
        if (this.age > user.age){
            return 1;
        }else if (this.age < user.age){
            return -1;
        }else {
            return this.name.compareTo(user.name);
        }
    }
}
// Demo.java 测试程序

public class Demo {


    public static void main(String[] args) {
        List<User> users = new ArrayList<>();
        int lastAge = -1;
        for (int i = 0; i < 20; i++) {
            User user = new User();
            if (lastAge==-1){
                int number = (int) (Math.random() * 100);
                user.setAge(number);
                lastAge = number;
            }else {
                user.setAge(lastAge);
                lastAge = -1;
            }
            int n = 20 - i;
            user.setName(n + "haha");
            user.setPass(n + "");
            users.add(user);
        }
        Collections.sort(users);
        for (int i = 0; i < 20; i++) {
            User user = users.get(i);
            System.out.println(user.getName() + " " + user.getAge() + " " + user.getPass());
        }
    }
}

调用排序，只需要Collections.sort(users); 即可。运行结果：略