java List集合中元素排序

1、java8

Person person1 = new Person("tom", 15);
Person person2 = new Person("jack", 26);
Person person3 = new Person("lucy", 12);

List<Person> list = Arrays.asList(person1,person2,person3);

//正序　　　　　　       　　　　　 
list.stream().sorted(Comparator.comparing(Person::getAge))
.collect(Collectors.toList()).forEach(person -> {
            System.out.println(person.getAge());
});

//倒序 　　　　　　
list.stream().sorted(Comparator.comparing(Person::getAge).reversed())
.collect(Collectors.toList()).forEach(person -> {
            System.out.println(person.getAge());
})；

2、Collections.sort(）方法进行简单排序

List<Integer> list = new ArrayList<Integer>();
list.add(new Integer(5));
list.add(new Integer(13));
list.add(new Integer(4));
list.add(new Integer(9));
Collections.sort(list);
System.out.println(list.toString());

输出结果：[4, 5, 9, 13]

3、list参数类型相对复杂的排序　　

List<User> list = new ArrayList<User>();
list.add(new User("张三", 5));
list.add(new User("李四", 30));
list.add(new User("王五", 19));
list.add(new User("赵六", 17));
Collections.sort(list); // 按年龄排序
System.out.println(list.toString());


//实体类实现Comparable 接口
class User implements Comparable<User> {

    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public int compareTo(User o) {
        return this.age - o.age;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

4、匿名内部类实现排序

List<User> list = new ArrayList<User>();
list.add(new User("张三", 5));
list.add(new User("李四", 30));
list.add(new User("王五", 19));
list.add(new User("赵六", 17)); 
Collections.sort(list, new Comparator<User>() {
            @Override
            public int compare(User u1, User u2) {
                int tmp = u1.getAge() - u2.getAge();
                if (tmp > 0) {
                    return 1;
                } else if (tmp < 0) {
                    return -1;
                }
                return 0; //相等为0
            }
}); // 按年龄排序
System.out.println(list.toString());