1、首先介绍Stream流排序, 因为这个玩意真的太方便了

public class SortDemo {public static void main(String[] args) {List<User> list = new ArrayList<>();list.add(new User(5, "张三"));list.add(new User(2, "李四"));list.add(new User(3, "王五"));List<User> result = list.stream().sorted(Comparator.comparingInt(u -> u.id)).collect(Collectors.toList());System.out.println(result); }static class User{private Integer id;private String name;public User(Integer id, String name) {this.id = id;this.name = name;}}
}

2、自己项目中类可以是实现Comparable接口, 这样就可以借用java自带的排序api, 比如Collections, TreeSet等

public class SortDemo {public static void main(String[] args) {TreeSet<User> treeSet = new TreeSet<>();treeSet.add(new User(5, "张三"));treeSet.add(new User(2, "李四"));treeSet.add(new User(3, "王五"));System.out.println(treeSet);}static class User implements Comparable<User>{private Integer id;private String name;public User(Integer id, String name) {this.id = id;this.name = name;}@Overridepublic int compareTo(User o) {return this.id - o.id;}@Overridepublic String toString() {return "User{" +"id=" + id +", name='" + name + '\'' +'}';}}
}

3、如果是二方/三方包中类可以基于Comparator接口, 这样也可以借用java自带的排序api

// 1中stream流中就是借用了这个接口
public static void main(String[] args) {List<User> list = new ArrayList<>();list.add(new User(5, "张三"));list.add(new User(2, "李四"));list.add(new User(3, "王五"));List<User> result = list.stream().sorted(Comparator.comparingInt(u -> u.id)).collect(Collectors.toList());System.out.println(result); 
}