从int -operator量数组中创建地图＆＃x27;％＆＃x27;不能应用于java.lang.object＆＃x27;

发布于 2025-02-05 02:55:57 字数 746 浏览 3 评论 0原文

我有这样的代码，应该从整数数组中创建MAP。键表示数字的数量。

public static Map<Integer, List<String>> groupByDigitNumbersArray(int[] x) {
    return Arrays.stream(x)  // array to stream
        .filter(n -> n >= 0) // filter negative numbers
        .collect(Collectors.groupingBy(n -> Integer.toString((Integer) n).length(), // group by number of digits
            Collectors.mapping(d -> (d % 2 == 0 ? "e" : "o") + d,
                Collectors.toList()))); // if even e odd o add to list
}

问题在于mapping（）。我遇到了一个错误：

Operator '%' cannot be applied to 'java.lang.Object', 'int'

有人知道如何解决这个问题吗？

原文

I have code like this, which is supposed to create a Map from an array of integers. The key represents the number of digits.

public static Map<Integer, List<String>> groupByDigitNumbersArray(int[] x) {
    return Arrays.stream(x)  // array to stream
        .filter(n -> n >= 0) // filter negative numbers
        .collect(Collectors.groupingBy(n -> Integer.toString((Integer) n).length(), // group by number of digits
            Collectors.mapping(d -> (d % 2 == 0 ? "e" : "o") + d,
                Collectors.toList()))); // if even e odd o add to list
}

The problem is in the line with mapping().
I'm getting an error:

Operator '%' cannot be applied to 'java.lang.Object', 'int'

Does someone know how to solve this?

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

金兰素衣 2025-02-12 02:55:57

collect> collect（） 期望collector作为参数， oprive streams < /em>。即使没有模量运算符％，您的代码也不会编译 - 评论 downstream collector groupingby（）以查看我在说什么关于。

您需要应用boxed（）操作，以便将intstream转换为对象流stream＆lt; integer＆gt;。

您的方法可能看起来像这样：

public static Map<Integer, List<String>> groupByDigitNumbersArray(int[] x) {
    
    return Arrays.stream(x)  // creates a stream over the given array
        .filter(n -> n >= 0) // retain positive numbers and zero
        .boxed()             // <- converting IntStream into a Stream<Integer>
        .collect(Collectors.groupingBy(
            n -> String.valueOf(n).length(), // group by number of digits
            Collectors.mapping(d -> (d % 2 == 0 ? "e" : "o") + d, // if even concatinate 'e', if odd 'o'
                Collectors.toList()))); // collect to list
}

我更改了classifier groupingby（）的功能更可读取。

The flavor of collect() that expects a Collector as an argument isn't available with primitive streams. Even without a modulus operator %, your code will not compile - comment out the downstream collector of groupingBy() to see what I'm talking about.

You need to apply boxed() operation in order to convert an IntStream into a stream of objects Stream<Integer>.

Your method might look like this:

public static Map<Integer, List<String>> groupByDigitNumbersArray(int[] x) {
    
    return Arrays.stream(x)  // creates a stream over the given array
        .filter(n -> n >= 0) // retain positive numbers and zero
        .boxed()             // <- converting IntStream into a Stream<Integer>
        .collect(Collectors.groupingBy(
            n -> String.valueOf(n).length(), // group by number of digits
            Collectors.mapping(d -> (d % 2 == 0 ? "e" : "o") + d, // if even concatinate 'e', if odd 'o'
                Collectors.toList()))); // collect to list
}

I've changed the classifier function of groupingBy() to be more readable.

回复收藏 0 原文

~没有更多了~