Java stream().reduce实现数组合并操作（数值累加、数值累减、数值求最大最小值、字符串连接）

àì夳堔傛蜴生んèń 2022-10-31 04:07 315阅读 0赞

### 1 数值累加 ###

int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    //lambda表达式实现
    int sum = Arrays.stream(numbers).reduce(0, (current, number) -> current + number);    // 55
    //方法引用实现
    int sum2 = Arrays.stream(numbers).reduce(0, Integer::sum);      // 55

注：更多类型的数值累加请参考以下博客。

[Java BigDecimal、Integer、Long、Double类型数值累加求和![icon-default.png?t=L892][icon-default.png_t_L892]https://blog.csdn.net/qq\_38974638/article/details/113913754][Java BigDecimal_Integer_Long_Double_icon-default.png_t_L892_icon-default.png_t_L892_https_blog.csdn.net_qq_38974638_article_details_113913754]

### 2 数值累减 ###

int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    //lambda表达式实现
    int sum = Arrays.stream(numbers).reduce(0, (current, number) -> current - number);    // -55

### 3 数值求最大最小值 ###

int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    //最大值
    int max = Arrays.stream(numbers).reduce(0, (current, number) -> current > number ? current : number);  // 10
    int max1 = Arrays.stream(numbers).reduce(0, Integer::max);            // 10
    //最小值
    int min = Arrays.stream(numbers).reduce(0, (current, number) -> current < number ? current : number);  // 0
    int min1 = Arrays.stream(numbers).reduce(0, Integer::min);            // 0

注：更多类型的数值求最大最小值请参考以下博客。

[Java BigDecimal、Integer、Long、Double类型数值求最大最小值![icon-default.png?t=L892][icon-default.png_t_L892]https://blog.csdn.net/qq\_38974638/article/details/120599044][Java BigDecimal_Integer_Long_Double_icon-default.png_t_L892_icon-default.png_t_L892_https_blog.csdn.net_qq_38974638_article_details_120599044]

###  4 字符串连接 ###

String[] strings = {"a", "b", "c", "d", "e"};
    
    // |a|b|c|d|e
    String reduce = Arrays.stream(strings).reduce("", (current, number) -> current + "|" + number);
    
    // a|b|c|d|e
    String reduce2 = Arrays.stream(strings).reduce("", (current, number) -> {
        if (!"".equals(current)) {
            return current + "|" + number;
        } else {
            return number;
        }
    });

注：更多字符串连接方法请参考以下博客。

[Java 字符串拼接4种实现方法（for循环、stream().reduce()、Collectors.joining()、String.join()）![icon-default.png?t=L892][icon-default.png_t_L892]https://blog.csdn.net/qq\_38974638/article/details/120604615][Java _4_for_stream_.reduce_Collectors.joining_String.join_icon-default.png_t_L892_icon-default.png_t_L892_https_blog.csdn.net_qq_38974638_article_details_120604615]

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[Java BigDecimal_Integer_Long_Double_icon-default.png_t_L892_icon-default.png_t_L892_https_blog.csdn.net_qq_38974638_article_details_113913754]: /images/20221024/695044f928f7457f9f2ff6646363adbf.png
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