Turn string values into 2d array of type double

Question

I have a string:

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

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

double [][] values = {{0, 4.28}, {10, 4.93}, {20, 3.75}};

I've formatted the string to remove any whitespace and replace with a comma:

String stringProfileFormatted = stringProfile.replaceAll(" ", ",");

So now String stringProfileFormatted = "0,4.28,10,4.93,20,3.75";

I then create a String array:

String[] array = stringProfileFormatted.split("(?<!\\G\\d+),");

So for every element in the Array is every 2 commas worth of string.

Not sure how to then convert into a 2d array. Is this even the right way to go about it?

Can you specify whether you mean multi-dimensional or 2-dimensional ? Your example is 2 dimensional, and my guess is you are interested in 2-dimentional arrays - Please correct to avoid confusion. Also are there any other helpful hints or assumptions that you can make ? Would the matrix be limited with a max dimension (would be reasonable to limit I think)? — Ely
– Ely, Commented Sep 13, 2018 at 14:15
Apologies, yes its a 2d array. Each array in the 2d Array would have fixed length of 2. It would be pairs as the example shows — arsenal88
– arsenal88, Commented Sep 13, 2018 at 14:18
If your string strictly follows the pattern shown in your input i.e. pair of two values comma separated and each such pair separated by space - then it is straightforward to solve this, just split the string by \\s+, then split each string in that splitted strings by "," then use Double.valueOf(string) to get double, create a new 1d array and insert it in your 2d array. Not sure if there is more complexity to this. — SomeDude
– SomeDude, Commented Sep 13, 2018 at 14:22

deHaar · Accepted Answer · 2018-09-13 14:40:50Z

7

I would go step by step resolving this task.

First, I would split the original String by a space, then split the results by comma each and afterwards create an array of double out of those values with Double.parseDouble(String value).

public static void main(String[] args) {
    String stringProfile = "0,4.28 10,4.93 20,3.75";

    // split it once by space
    String[] parts = stringProfile.split(" ");

    // create some result array with the amount of double pairs as its dimension
    double[][] results = new double[parts.length][];

    // iterate over the result of the first splitting
    for (int i = 0; i < parts.length; i++) {
        // split each one again, this time by comma
        String[] values = parts[i].split(",");

        // create two doubles out of the single Strings
        double a = Double.parseDouble(values[0]);
        double b = Double.parseDouble(values[1]);

        // add them to an array
        double[] value = {a, b};

        // add the array to the array of arrays
        results[i] = value;
    }

    // then print the result
    for (double[] pair : results) {
        System.out.println(String.format("%.0f and %.2f", pair[0], pair[1]));
    }
}

Yes, these are a lot of lines of code, but most likely more easily understandable than lambda expressions (which are cooler and more elegant in my opinion).

edited Sep 13, 2018 at 14:40

answered Sep 13, 2018 at 14:32

deHaar

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2 Comments

nabster Over a year ago

I would change print to System.out.println(String.format("%.0f and %.2f", pair[0], pair[1])); for better formatting. It prints unnecessary digits after decimal.

nabster Over a year ago

This 0 and 4.28 instead of 0.000000 and 4.280000

Anton Balaniuc · Accepted Answer · 2018-09-13 14:51:15Z

5

What about something like this:

Arrays.stream("0,4.28 10,4.93 20,3.75".split(" ")) //Stream<String>
     .map(s -> 
           Arrays.stream(s.split(",")) // take an individual string like 0,4.28  
                 .map(Double::parseDouble) // and transform it to a double array
                 .toArray(Double[]::new)
      )
     .toArray(Double[][]::new);

the result is

$8 ==> Double[3][] { 
        Double[2] { 0.0, 4.28 }, 
        Double[2] { 10.0, 4.93 }, 
        Double[2] { 20.0, 3.75 } 
}

edited Sep 13, 2018 at 14:51

answered Sep 13, 2018 at 14:29

Anton Balaniuc

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1 Comment

SomeDude Over a year ago

was just waiting for someone to come up with a one-liner using streams. :)

Schidu Luca · Accepted Answer · 2018-09-13 14:27:23Z

2

If your string follows the pattern you described then you do it like this:

String stringProfile = "0,4.28 10,4.93 20,3.75";
String[] split = stringProfile.split(" "); // split by space;

double[][] a = new double[split.length][]; // your result

for(int i = 0; i < split.length; i++) {
    String[] numbers = split[i].split(","); // split by ,
    double[] doubles = Arrays.stream(numbers).mapToDouble(Double::new).toArray(); //create 1-D array
    a[i] = doubles; // assign it do your result
}

answered Sep 13, 2018 at 14:27

Schidu Luca

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Comments

Susanna M · Accepted Answer · 2018-09-13 14:43:08Z

0

Assuming that your string strictly follows the given sample pattern, you can make use of the following code:

    String stringProfile = "0,4.28 10,4.93 20,3.75";
    stringProfile = stringProfile.replace(' ', ',');
    String [] strArry = stringProfile.split(",");
    double [][] doubleArray = new double [strArry.length/2][2];
    for(int i=0, j=0; i<strArry.length; i=i+2, j++) {
        doubleArray [j][0] = Double.valueOf(strArry[i]);
        doubleArray [j][1] = Double.valueOf(strArry[i+1]);
    }

answered Sep 13, 2018 at 14:43

Susanna M

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Comments

Luis Romero · Accepted Answer · 2018-09-13 14:25:36Z

-1

if you split with " " you get an array of one dimension, then you can split again and get a multidimensional array like you want:

String arrayS = "0,4.28 10,4.93 20,3.75";
String [] a = arrayS.spit(" ");
double [][] arrayD;
for(String j: a){
    arrayD.append(j.split(","));
}
//then print your array here

answered Sep 13, 2018 at 14:25

Luis Romero

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2 Comments

SomeDude Over a year ago

Are you sure there is a append on array ? Question is specific to Java.

Luis Romero Over a year ago

yeah, im confused, instead use add or push, im not remember what its, im only use arralist on java xd

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