集合排序（list）

1.Comparable自然规则排序
//在自定义类Student里面实现Comparable接口，并重写抽象方法compareTo(Student o);
//Collections.sort(集合);

    public static void main(String[] args) {
        List<Integer> nums = new ArrayList<Integer>();
            nums.add(3);
            nums.add(5);
            nums.add(1);
            nums.add(0);
            System.out.println(nums);
            Collections.sort(nums);
            System.out.println(nums);
    }

输出结果：
[3, 5, 1, 0]
[0, 1, 3, 5]

稍微复杂的List里面放一个复杂的对象

package core.java.collection.collections;

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());
        }
}

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