将字符串转换为多维数组 [英] Turn string into multidimensional array

问题描述

我有一个字符串：

String stringProfile = "0, 4.28 10, 4.93 20, 3.75";

我试图把它变成一个如下数组：

I am trying to turn it into an array like as follows:

double [][] values = {{FastMath.toRadians(0), FastMath.toRadians(4.28)},
                      {FastMath.toRadians(10), FastMath.toRadians(4.93)},
                      {FastMath.toRadians(20), FastMath.toRadians(3.75)}}; 

其中 FastMath.toRadians 是一个方法每个元素。

Where FastMath.toRadians is a method on each element.

问题数量：

首先要做的事情就是拆分字符串：

First logical thing to do is to split the string:

List<String> stringProfileList= Arrays.asList(stringProfile.split(" "));

输出为0,4.28,10,4.93,3， 3.75，所以现在每个元素都被，而不是其他元素分开。

The output would be "0, 4.28, 10, 4.93, 20, 3.75", so now every element is split by a "," rather than every other.

然后对于列表中的每2个元素，我需要分配一个数组。
在每个数组中，我在每个元素上应用FastMath.toRadians（），然后将每个数组附加到一个更大的多维数组。

Then for every 2 elements in the list, I need to assign to an array. Within each Array I apply the FastMath.toRadians() on each element and then I append each array to a larger multidimensional array.

这是正确的方法这个怎么样？我正在坚持实现每2个元素。

Is this the right way to go about this? I'm getting stuck at implementing for every 2 elements.

我还需要将这些字符串元素转换为double，这似乎并不重要。

I also need to convert these string elements into a double, which doesn't seem to trivial.

推荐答案

如果你想使用 Stream 试试这个：

If you want to use Stream try this:

    Pattern PAIR = Pattern.compile("(?<=\\d)\\s(?=\\d)");

    double[][] result = PAIR.splitAsStream(stringProfile)
            .map(pair -> pair.split(","))
            .map(pair -> new double[] { FastMath.toRadians(Double.valueOf(pair[0])), FastMath.toRadians(Double.valueOf(pair[1])) })
            .toArray(i -> new double[i][]);

A 模式用于拆分 stringProfile 在空白字符上有后面的数字和提前它们。这会产生一个 Stream 的字符串，其中包含一对数字除以'，'。我们拆分第一个地图中的'，'上的这个字符串获取表示数字的字符串数组。在下一个 map 中，解析的数字和它们的弧度被计算出来。

A Pattern is used to split stringProfile on whitespace characters which have a digit behind and ahead them. This results in a Stream of strings which contains a pair of numbers divided by ', '. We split this string on ',' in a first map to get an array of strings representing the numbers. In the next map the numbers a parsed and their radians is computed.

我们可以解析数字以及弧度到单个 map 步骤的共同点。以下代码更详细，但创建了一个额外的双数组：

We could devide the parsing of the numbers and the comuputation of the radians to single map steps. The following code is more verbose but creates an additional double array:

double[][] result = PAIR.splitAsStream(stringProfile)
        .map(pair -> pair.split(","))
        .map(pair -> new double[] { Double.valueOf(pair[0]), Double.valueOf(pair[1]) })
        .map(pair -> new double[] { FastMath.toRadians(pair[0]), FastMath.toRadians(pair[1]) })
        .toArray(i -> new double[i][]);

如果我们想重用双数组，我们可以这样做：

If we want to reuse the double array, we can do this like this:

        .map(pair -> {
            pair[0] = FastMath.toRadians(pair[0]);
            pair[1] = FastMath.toRadians(pair[1]);
            return pair;
        })

最后一步将双数组收集到一个二维数组中。

The last step collects the double arrays into a two dimensional array.

编辑：

查看此演示。

使用模式类使用的模式查找空白字符（ \\\\ ）之前（（？< = \\d） = 看后面）并成功（（？= \\d） = 展望未来）电子数字（ \\\\ ）。这些外观具有零宽度，因此它们被评估为捕获（匹配）但不是匹配序列的一部分（ Matcher.group（ ） ）。 匹配序列仅包含空格字符（ \\\\ ）。

Using the wording of the documentation of the Pattern class the used pattern looks for a whitespace character (\\s) which is preceded ((?<=\\d) = look behind) and succeeded ((?=\\d) = look ahead) by one digit (\\d). These looks have zero-width, thus they are evaluated for capturing (matching) but are not part of the matched sequence (Matcher.group()). The matching sequence contains only a whitespace character (\\s).

对于 stringProfile 这种模式在两种情况下匹配：8 1和3 2。在这些情况下，两个数字围绕。另一方面，例如0,4不匹配。 ，的出现会阻止匹配。

For stringProfile this pattern will match in two cases: "8 1" and "3 2". In these cases two digits are surrounding a " ". On the other hand e.g. "0, 4" doesn't match. The occurrence of "," prevents a match.

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