lambda表达式处理集合的一些使用例子

@Data
    public static class Student{
        private String id;
        private String name;
        private Double score;
        private Integer age;
        private Integer sex;
    }

    public static void main(String[] args) {
        //过滤
        List<Student> listFilter = list.stream().filter(item -> item.getAge() > 14)
                .collect(Collectors.toList());
        System.out.println("过滤:"+JSONArray.toJSONString(listFilter));
     
        //排序
        List<Student> sortedList = list.stream().sorted(Comparator.comparing(Student::getScore).reversed()).collect(Collectors.toList());
        //正序List<Student> sortedList = list.stream().sorted(Comparator.comparing(Student::getScore)).collect(Collectors.toList());
        System.out.println("分数排行："+JSONArray.toJSONString(sortedList));
      
        //过滤并排序
        List<Student> listFilterSort = list.stream().filter(item -> item.getAge() > 14)
                .sorted(Comparator.comparing(Student::getScore))
                .collect(Collectors.toList());
        System.out.println("过滤排序:"+JSONArray.toJSONString(listFilterSort));
      
        //求总分
        double sum = list.stream().mapToDouble(Student::getScore).sum();
        System.out.println("总分："+JSONArray.toJSONString(sum));
     
        //获取list某个字段组装新list
        List<String> nameList = list.stream().map(item -> item.getName()).collect(Collectors.toList());
        System.out.println("学生名单："+ JSONArray.toJSONString(nameList));
        
        //去重
        List<Student> disList = list.stream().collect(
                Collectors.collectingAndThen(
                        Collectors.toCollection(() -> new TreeSet<>(Comparator
                                .comparing(Student::getName))), ArrayList::new));
        System.out.println("去重:"+JSONArray.toJSONString(disList));
       
        //分组
        Map<Integer, List<Student>> groupList = list.stream().collect(Collectors.groupingBy(Student::getSex));
        System.out.println("分组:"+JSONArray.toJSONString(groupList));
        
        //根据两个属性去重
        List<Student> disTwo = list.stream().collect(
                Collectors.collectingAndThen(
                        Collectors.toCollection(() -> new TreeSet<>(
                                Comparator.comparing(o -> o.getId() + ";" + o.getSex()))), ArrayList::new));
        System.out.println("根据两个属性去重："+JSONArray.toJSONString(disTwo));
        //基本类型列表去重
        List<Long> li = versionIds.stream().distinct().collect(Collectors.toList());
    }
  

过滤:[{"age":15,"id":"1","name":"李四","score":95.5,"sex":0},{"age":16,"id":"2","name":"张三","score":90,"sex":1},{"$ref":"$[0]"},{"$ref":"$[1]"}]
分数排行：[{"age":15,"id":"1","name":"李四","score":95.5,"sex":0},{"age":16,"id":"2","name":"张三","score":90,"sex":1},{"age":14,"id":"2","name":"王二","score":85.5,"sex":1},{"age":14,"id":"2","name":"王二","score":85.5,"sex":1}]
过滤排序:[{"age":16,"id":"2","name":"张三","score":90,"sex":1},{"age":15,"id":"1","name":"李四","score":95.5,"sex":0}]
总分：356.5
学生名单：["李四","张三","王二","王二"]
去重:[{"age":16,"id":"2","name":"张三","score":90,"sex":1},{"age":15,"id":"1","name":"李四","score":95.5,"sex":0},{"age":14,"id":"2","name":"王二","score":85.5,"sex":1}]
分组:{0:[{"age":15,"id":"1","name":"李四","score":95.5,"sex":0}],1:[{"age":16,"id":"2","name":"张三","score":90,"sex":1},{"age":14,"id":"2","name":"王二","score":85.5,"sex":1},{"age":14,"id":"2","name":"王二","score":85.5,"sex":1}]}
根据两个属性去重：[{"age":15,"id":"1","name":"李四","score":95.5,"sex":0},{"age":16,"id":"2","name":"张三","score":90,"sex":1}]