jdk8 新特性之 Stream流

骑猪看日落 2023-03-13 13:17 81阅读 0赞

## 1、第一个使用流示例 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70]

## 2、获取流 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 1]

## 3、过滤流 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 2]

## 4 、映射流 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 3]

## 5 、取前几个 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 4]

## 6、跳过前几个 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 5]

## 7 、先跳过前几个, 在获取跳过后的前几个，（类似于分页） ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 6]

## 8、将流转为集合 `collect`（Map/ List） ##

转 list  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 7]  
转map

// value 等于对象
    Map<Integer, Student> map = list.stream().collect(Collectors.toMap(Student::getId, student -> student));
    
    // value 等于对象的某个值
    Map<Integer, String> map = list.stream().collect(Collectors.toMap(Student::getId, Student::getName));

## 9 、合并流 concat ##

![在这里插入图片描述][20200514082048355.png]

## 10、练习 demo ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 8]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNDYzNjU1_size_16_color_FFFFFF_t_70 9]  
![在这里插入图片描述][20200514082048355.png]

## 11、统计查询 ##

统计查询 (针对 List集合, stream()方式)  
[https://blog.csdn.net/qq\_41463655/article/details/106068287][https_blog.csdn.net_qq_41463655_article_details_106068287]

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[20200514082048355.png]: https://img-blog.csdnimg.cn/20200514082048355.png
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[https_blog.csdn.net_qq_41463655_article_details_106068287]: https://blog.csdn.net/qq_41463655/article/details/106068287