工作记录------Stream排序应用

╰+攻爆jí腚メ 2024-03-27 14:05 16阅读 0赞

## 工作记录------Stream排序应用 ##

顺序、逆序、多条件排序  
DTO

@Data
            @ToString
            class Teacher{
        
                private  Integer id;
                private  String name;
                private  Integer age;
                private  Integer tall;
                private  Date birthday;
            }

集合：

List<Teacher> teacherList = new ArrayList<>();
            Teacher teacher = new Teacher();
            teacher.setId(1);
            teacher.setAge(10);
            teacher.setName("张一");
            Teacher teacher2 = new Teacher();
            teacher2.setId(2);
            teacher2.setAge(20);
            teacher2.setName("李二");
            Teacher teacher3 = new Teacher();
            teacher3.setId(3);
            teacher3.setAge(30);
            teacher3.setName("王三");
            Teacher teacher4 = new Teacher();
            teacher4.setId(1);
            teacher4.setAge(30);
            teacher4.setName("赵四");
            teacherList.add(teacher);
            teacherList.add(teacher2);
            teacherList.add(teacher3);
            teacherList.add(teacher4);

### 升序排序，年龄升序 ###

按照年龄  
Comparator.comparing（放实体类名称::放列名）：添加排序字段；

teacherList.stream().sorted(Comparator.comparing(Teacher::getAge))
                    .forEach(System.out::println);

输出结果：

Teacher(id=1, name=张一, age=10, tall=null, birthday=null)
    Teacher(id=2, name=李二, age=20, tall=null, birthday=null)
    Teacher(id=3, name=王三, age=30, tall=null, birthday=null)
    Teacher(id=1, name=赵四, age=30, tall=null, birthday=null)

### 降序排序，年龄降序 ###

按照年龄  
Comparator.reverseOrder() ：降序排序

teacherList.stream().sorted(Comparator.comparing(Teacher::getAge,reverseOrder()))
                    .forEach(System.out::println);

输出结果：

Teacher(id=3, name=王三, age=30, tall=null, birthday=null)
    Teacher(id=1, name=赵四, age=30, tall=null, birthday=null)
    Teacher(id=2, name=李二, age=20, tall=null, birthday=null)
    Teacher(id=1, name=张一, age=10, tall=null, birthday=null)

### 多条件排序，先按照年龄升序，再ID升序 ###

通过在Comparator.comparing()后，再调用thenComparing方法。

teacherList.stream().sorted(
                    Comparator.comparing(Teacher::getAge)
                            .thenComparing(Teacher::getId))
                    .forEach(System.out::println);

输出结果：

Teacher(id=1, name=张一, age=10, tall=null, birthday=null)
    Teacher(id=2, name=李二, age=20, tall=null, birthday=null)
    Teacher(id=1, name=赵四, age=30, tall=null, birthday=null)
    Teacher(id=3, name=王三, age=30, tall=null, birthday=null)

### 多条件排序，先按照ID升序，再年龄降序 ###

同理，只是对需要降序的字段，传入reverseOrder()。

teacherList.stream().sorted(
                    Comparator.comparing(Teacher::getId)
                            .thenComparing(Teacher::getAge,reverseOrder()))
                    .forEach(System.out::println);

结果：

Teacher(id=1, name=赵四, age=30, tall=null, birthday=null)
    Teacher(id=1, name=张一, age=10, tall=null, birthday=null)
    Teacher(id=2, name=李二, age=20, tall=null, birthday=null)
    Teacher(id=3, name=王三, age=30, tall=null, birthday=null)

### 多条件排序，先按照ID降序，再年龄升序 ###

teacherList.stream().sorted(
                    Comparator.comparing(Teacher::getId,reverseOrder())
                            .thenComparing(Teacher::getAge))
                    .forEach(System.out::println);

输出结果：

Teacher(id=3, name=王三, age=30, tall=null, birthday=null)
    Teacher(id=2, name=李二, age=20, tall=null, birthday=null)
    Teacher(id=1, name=张一, age=10, tall=null, birthday=null)
    Teacher(id=1, name=赵四, age=30, tall=null, birthday=null)

### 多条件排序，先按照ID降序，再年龄降序 ###

teacherList.stream().sorted(
                    Comparator.comparing(Teacher::getId,reverseOrder())
                            .thenComparing(Teacher::getAge,reverseOrder()))
                    .forEach(System.out::println);

输出结果：

Teacher(id=3, name=王三, age=30, tall=null, birthday=null)
    Teacher(id=2, name=李二, age=20, tall=null, birthday=null)
    Teacher(id=1, name=赵四, age=30, tall=null, birthday=null)
    Teacher(id=1, name=张一, age=10, tall=null, birthday=null)

### 如需要再增加排序的条件，只需要再增加.thenComparing()方法即可。 ###

以上对排序的操作，能够应对工作中大部分需要排序的情况