jdk8 stream示例

//跟据某个属性分组
        Map<String, List<PersonData>> collect = list.stream().collect(Collectors.groupingBy(PersonData::getType));
        System.out.println(collect);
        
        //根据某个属性分组，汇总某个属性
        Map<String, Integer> collect2 = list.stream().collect(Collectors.groupingBy(PersonData::getType,Collectors.summingInt(PersonData::getAge)));
        System.out.println(collect2);
        
        //根据某个属性添加条件过滤数据，
        list = list.stream().filter(u -> !u.getType().equals("访客")).collect(Collectors.toList());
        System.out.println(list);
        
        //判断一组对象里面有没有属性值是某个值
        boolean add = list.stream().anyMatch(m -> "王五".equals(m.getName()));
        System.out.println(add);
        
        //取出一组对象的某个属性组成一个新集合
        List<String> names=list.stream().map(PersonData::getName).collect(Collectors.toList());
        System.out.println(names);
    }