Java parsing command line arguments ( args[]) into an int[][] Type

In the program arguments using a space splits it into two different arguments. What would probably be best for you is to change it to the format to:

1,2;0,3;3,4;3,4

Then

String[] firstMatrix = args[0].split(";");
System.out.print(Arrays.toString(firstMatrix));

Produces

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

And doing

int[][] ints = new int[firstMatrix.length][2];
int[] intsInside;
for (int i = 0; i < firstMatrix.length; i++) {
    intsInside  = new int[2];
    intsInside[0] = Integer.parseInt(firstMatrix[i].split(",")[0]);
    intsInside[1] = Integer.parseInt(firstMatrix[i].split(",")[1]);
    ints[i] = intsInside;
}

System.out.print("\n" + Arrays.deepToString(ints));

Produces

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

NOTE: Values 0, 1, and 2 in certain places in the code should be replaced with dynamic values based on array lengths etc.

As you have provided arguments like "1,2;0,3 3,4;3,4", it seems you will have args[0] and args[1] as two-parameter for input but you have only shown args[0] in your example. Below is a modified version of your code which might give you hint for your solution

public static void main(String[] args) {
    for (String tmpString : args) {
        String[] firstmatrix = tmpString.split(";");

  // Assuming that only two elements will be there splitter by `,`. 
        // If not the case, you have to add additional logic to dynamically get column length

    String[][] rowNumbers = new String[firstmatrix.length][2];
        for (int i = 0; i < firstmatrix.length; i++) {
            rowNumbers[i] = firstmatrix[i].split(",");
        }
    }
}

You can try something like splitting the input by semicolon first in order to get the rows of the matrix and then split each row by comma in order to get the single values of a row.

The following example does exactly that:

public static void main(String[] args) {
    System.out.println("Please enter the matrix values");
    System.out.println("(values of a row delimited by comma, rows delimited by semicolon, example: 1,2;3,4 for a 2x2 matrix):\n");
    // fire up a scanner and read the next line
    try (Scanner sc = new Scanner(System.in)) {
        String line = sc.nextLine();
        // split the input by semicolon first in order to have the rows separated from each other
        String[] rows = line.split(";");
        // split the first row in order to get the amount of values for this row (and assume, the remaining rows have this size, too
        int columnCount = rows[0].split(",").length;
        // create the data structre for the result
        int[][] result = new int[rows.length][columnCount];
        // then go through all the rows
        for (int r = 0; r < rows.length; r++) {
            // split them by comma
            String[] columns = rows[r].split(",");
            // then iterate the column values,
            for (int c = 0; c < columns.length; c++) {
                // parse them to int, remove all whitespaces and put them into the result
                result[r][c] = Integer.parseInt(columns[c].trim());
            }
        }

        // then print the result using a separate static method
        print(result);
    }
}

The method that prints the matrix takes an int[][] as input and looks like this:

public static void print(int[][] arr) {
    for (int r = 0; r < arr.length; r++) {
        int[] row = arr[r];
        for (int v = 0; v < row.length; v++) {
            if (v < row.length - 1)
                System.out.print(row[v] + " | ");
            else
                System.out.print(row[v]);
        }
        System.out.println();
        if (r < arr.length - 1)
            System.out.println("—————————————");
    }
}

Executing this code and inputting the values 1,1,1,1;2,2,2,2;3,3,3,3;4,4,4,4 results in the output

1 | 1 | 1 | 1
—————————————
2 | 2 | 2 | 2
—————————————
3 | 3 | 3 | 3
—————————————
4 | 4 | 4 | 4

I tried the java8 stream way, with int[][] as result

String s = "1,2;0,3;3,4;3,4";
int[][] arr = Arrays.stream(s.split(";")).
       map(ss -> Stream.of(ss.split(","))
            .mapToInt(Integer::parseInt)
            .toArray())
       .toArray(int[][]::new);

With List<List<Integer>>, should be the same effect.

String s = "1,2;0,3;3,4;3,4";
        List<List<Integer>> arr = Arrays.stream(s.split(";")).
                map(ss -> Stream.of(ss.split(","))
                        .map(Integer::parseInt)
                        .collect(Collectors.toList()))
                .collect(Collectors.toList());
        System.out.println(arr);

Hope it helps