I have a simple 2d array

// Creating and Initializing 2D array
        int a[][] = {{0,1},{2,3},{4,5}};
        for(int i=0; i<3; i  ) {
            for(int j=0; j<2; j  ) {
                System.out.print(a[i][j] " ");
            }
            System.out.println();
        }

works everything fine. But how can I initialize the array when the content is dynamic and coming from a variable?

String arrContent = "{{0,1},{2,3},{4,5}}"; //actually a method readContentFromFile(); will deliver the content
int a[][] = arrContent;

Is there any way to do this?

CodePudding user response：

The input stream can be parsed using String::split and Stream API:

1. get rows splitting by comma between a pair of },{
2. remove redundant curly brackets using String::replaceAll
3. for each row, split by comma, convert numbers to int Stream::mapToInt and get array
4. collect to multidimensional array with Stream::toArray

String arrContent = "{{0,1},{2,3},{4,5}}";

int[][] arr = Arrays.stream(arrContent.split("\\}\\s*,\\s*\\{")) //1
    .map(s -> s.replaceAll("[{}]", ""))                          //2
    .map(s -> Arrays.stream(s.split("\\s*,\\s*"))                //3
                    .mapToInt(Integer::parseInt).toArray()
    )
    .toArray(int[][]::new);                                      //4
    
System.out.println(Arrays.deepToString(arr));

Output

[[0, 1], [2, 3], [4, 5]]

Another approach could be to use JSON parser, however, initial input string needs to be modified to become a valid JSON array (curly brackets {} have to be replaced with the square ones [] using simpler String::replace(char old, char rep)):

String arrContent = "{{0,1},{2,3},{4,5}}";

ObjectMapper om = new ObjectMapper();

int[][] arr = om.readValue(
        arrContent.replace('{', '[')
                  .replace('}', ']'),
        int[][].class);

System.out.println(Arrays.deepToString(arr));

// output
[[0, 1], [2, 3], [4, 5]]

CodePudding user response：

Just wanted to provide a little bit modified solution using simple regexp just in case anybody would prefer doing it this way:

String input = "{{0,1},{2,3},{4,5}}";
Pattern pattern = Pattern.compile("\\{[0-9,] }");
int[][] array = pattern.matcher(input).results()
    .map(matchResult -> matchResult.group().replaceAll("[{}]", ""))
    .map(numberAsText -> Arrays.stream(numberAsText.split(",")).mapToInt(Integer::parseInt).toArray())
    .toArray(int[][]::new);

Just as the others pointed out - if you have the possibility to change shape of input - I would also advice to use JSON's array and parse it using JSON parser which would make it much easier and more clean.