Java List集合排序的两种方法

Posted 2021-03-20 路上的风景

1.使用 Collections 工具类中的 sort() 方法

　　参数不同： void sort(List list) 在自定义类User里面实现Comparable<User>接口，并重写抽象方法compareTo(Student o);
　　　　　　　 void sort(List list, Comparator c) 第二个参数为了省事，可以直接使用匿名内部类

public class User implements Comparable<User>{  
      
    private int score;  
      
    private int age;  
      
    public User(int score, int age){  
        super();  
        this.score = score;  
        this.age = age;  
    }  
  
    public int getScore() {  
        return score;  
    }  
  
    public void setScore(int score) {  
        this.score = score;  
    }  
  
    public int getAge() {  
        return age;  
    }  
  
    public void setAge(int age) {  
        this.age = age;  
    }  
  
    @Override  
    public int compareTo(User o) {  
        int i = this.getAge() - o.getAge();//先按照年龄排序  
        if(i == 0){  
            return this.score - o.getScore();//如果年龄相等了再用分数进行排序  
        }  
        return i;  
    }  
      
}  
  
public static void main(String[] args) {  
        List<User> users = new ArrayList<User>();  
        users.add(new User(78, 26));  
        users.add(new User(67, 23));  
        users.add(new User(34, 56));  
        users.add(new User(55, 23));  
        Collections.sort(users);  
        for(User user : users){  
            System.out.println(user.getScore() + "," + user.getAge());  
        }  
}

public class Students {  
      
    private int age;  
    private int score;  
      
    public Students(int age, int score){  
        super();  
        this.age = age;  
        this.score = score;  
    }  
      
    public int getAge() {  
        return age;  
    }  
    public void setAge(int age) {  
        this.age = age;  
    }  
    public int getScore() {  
        return score;  
    }  
    public void setScore(int score) {  
        this.score = score;  
    }  
}  
public static void main(String[] args) {  
        List<Students> students = new ArrayList<Students>();  
        students.add(new Students(23, 100));  
        students.add(new Students(27, 98));  
        students.add(new Students(29, 99));  
        students.add(new Students(29, 98));  
        students.add(new Students(22, 89));  
        Collections.sort(students, new Comparator<Students>() {  
  
            @Override  
            public int compare(Students o1, Students o2) {  
                int i = o1.getScore() - o2.getScore();  
                if(i == 0){  
                    return o1.getAge() - o2.getAge();  
                }  
                return i;  
            }  
        });  
        for(Students stu : students){  
            System.out.println("score:" + stu.getScore() + ":age" + stu.getAge());  
        }  
}

2.直接使用list.sort()方法，传入实现Comparator接口的实现类的实例，为了省事直接传入匿名内部类

public class Students {

    private int age;
    private int score;

    public Students(int age, int score){
        this.age = age;
        this.score = score;
    }

    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public int getScore() {
        return score;
    }
    public void setScore(int score) {
        this.score = score;
    }
}
public static void main(String[] args) {
　　List<Students> students = new ArrayList<Students>();
　　students.add(new Students(23, 100));
　　students.add(new Students(27, 98));
　　students.add(new Students(29, 99));
　　students.add(new Students(29, 98));
　　students.add(new Students(22, 89));

　　students.sort(new Comparator<Students>() {
　　　　@Override
　　　　public int compare(Students o1, Students o2) {
　　　　　　int i = o1.getScore() - o2.getScore();
　　　　　　if (i == 0) {
　　　　　　　　return o1.getAge() - o2.getAge();
　　　　　　}
　　　　　　return i;
　　　　}
　　});

　　for (Students stu : students) {
　　　　System.out.println("score:" + stu.getScore() + ":age" + stu.getAge());
　　}
}