按list中某个属性排序，sort，collections类，sort规则。

我就是我 2023-10-10 14:46 16阅读 0赞

在排序的时候，给sort()方法传入一个比较器。传入一个实现比较器接口的匿名内部类，告诉sort()方法按照比较器来对list中的对象进行排序。如下所示：

public class Test 
    {
        public static void main(String[] args) 
        {
            ArrayList<Entity> list=new ArrayList<Entity>();
            list.add(new Entity("余涛",24));
            list.add(new Entity("王宁",13));
            list.add(new Entity("崔同发",25));
            System.out.println("排序前："+list);
            Collections.sort(list,new Comparator<Entity>() {
            @Override
            public int compare(Entity o1, Entity o2) 
            {
                if(o1.getAge()>o2.getAge())
                {
                    //返回1为o1放在后面
                    return 1;
                }
                else if(o1.getAge()<o2.getAge())
                {
                    //返回-1为o1放在前面
                    return -1;
                }
                else
                {
                    //返回0代表不排序，按之前的排序方法
                    return 0;
                }
            }
        });
            System.out.println("排序后："+list);
        }
    }
    class Entity
    {
        String name;
        int age;
        public Entity(String name, int age) {
            super();
            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 String toString() {
            return "Entity [name=" + name + ", age=" + age + "]";
        }
    }

排序前：[Entity [name=余涛, age=24], Entity [name=王宁, age=13], Entity [name=崔同发, age=25]]
    排序后：[Entity [name=王宁, age=13], Entity [name=余涛, age=24], Entity [name=崔同发, age=25]]

sort方法：

//返回1为o1放在后面
    return 1;
    //返回-1为o1放在前面
    return -1;
    //map对象转换为VO对象集合
    //返回0代表不排序，按之前的排序方法
    return 0;

业务场景：

//按是否含有分配任务（icedMemberManagementVO.getInvolveProject()字段是否为空）排序
                Collections.sort(result, new Comparator<ICEDMemberVO>() {
                    @Override
                    public int compare(ICEDMemberVO o1, ICEDMemberVO o2) {
                        List<ICEDMemberManagementVO> icedMemberManagementVOS1 = o1.getIcedMemberManagementVOS();
                        List<ICEDMemberManagementVO> icedMemberManagementVOS2 = o2.getIcedMemberManagementVOS();
                        Integer a = 0;
                        Integer b = 0;
                        for (ICEDMemberManagementVO icedMemberManagementVO : icedMemberManagementVOS1){
                            if (StringUtils.isNotBlank(icedMemberManagementVO.getInvolveProject())){
                                a = 1;
                            }
                        }
                        for (ICEDMemberManagementVO icedMemberManagementVO : icedMemberManagementVOS2){
                            if (StringUtils.isNotBlank(icedMemberManagementVO.getInvolveProject())){
                                b = 1;
                            }
                        }
                        if (a == 0 && b == 0){
                            return 0;
                        }else if ( a == 1 && b == 1){
                            return 0;
                        }else if (a == 1){
                            return -1;
                        }else {
                            return -1;
                        }
                    }
                });