CODEWITHSUNDEEP
javaarraysmatrixmultidimensional-array
jorge_brains
jorge_brains

Reputation: 13

Fill rows of 2D array with input from a String

I have the following issue: The values of each row of my matrix are given, with columns separated by a whitespace - so I enter all row values in a String array, remove the white spaces and parse the numbers into an int array. Now the values of each row look like 1 number "12345", while they should be "1 2 3 4 5".

How can I first separate the digits and then fill my matrix by adding the elements to each row? Thanks! Here is my code: 

    String n1 = input.nextLine ();
    int n = Integer.parseInt(n1); //rows of the matrix
    String[] arr = new String [n]; //contains all the rows of the matrix
    int [] array = new int [arr.length]; // contains all the elements of the rows of the matrix without whitespace

    for (int i = 0; i < arr.length; i++) {
        arr [i] = input.nextLine().replaceAll("\\s+","");
        array[i] = Integer.parseInt(arr[i]);
    }

    int matrix [][] = new int [n][arr[0].length()];

Upvotes: 1

Views: 1824

Answers (3)

nilx1
nilx1

Reputation: 26

It is hard to say but as i understand, you're trying to input a matrix line by line via the Scanner. This could solve your problem.

    Scanner scanner = new Scanner(System.in);
    //number of rows
    int n = Integer.parseInt(scanner.nextLine());
    int[][] matrix = new int[n][];
    for(int i=0;i<n;i++) {
        String line = scanner.nextLine();
        String[] numbers = line.split(" ");
        matrix[i] = new int[numbers.length];
        for(int j=0;j<numbers.length;j++) {
            matrix[i][j] = Integer.parseInt(numbers[j]);
        }
    }

Upvotes: 1

davidxxx
davidxxx

Reputation: 131346

Here you have important issues :

for (int i = 0; i < arr.length; i++) {
    arr [i] = input.nextLine().replaceAll("\\s+",""); // loses the separator between the number
    array[i] = Integer.parseInt(arr[i]); // makes no sense as you want get all numbers submitted for the current row and no a single one
}

You could do the processing by using much less variables if you populate the matrix at each row submitted.
No tested code but you should get an idea. 

String n1 = input.nextLine();
int n = Integer.parseInt(n1); //rows of the matrix  

int matrix [][] = null; // init it later : as you would have the two dimensions knowledge

for (int i = 0; i < n; i++) {
    String[] numberToken = input.nextLine().split("\\s"); 

    // matrix init : one time
    if (matrix == null){ matrix [][] = new int[n][numberToken.length]; }

    // array of int to contain numbers of the current row
    int[] array = new int[numberToken.length];

    // map String to int. Beware exception  handling that you should do
    for (int j = 0; j < numberToken.length; j++){
        array[j] = Integer.parseInt(numberToken[j]); 
    }
    // populate current row of the matrix
    matrix[i] = array[j];
}

Upvotes: 1

Boken
Boken

Reputation: 5446

You should split() input String by some char (space in your example).

Example how to convert String to array of String (using split() method)

// Example input
String input  = "1 2 3 4 5";

// Split elements by space
// So you receive array: {"1", "2", "3", "4", "5"}
String[] numbers = input.split(" ");

for (int position = 0; position < numbers.length; position++) {
    // Get element from "position"
    System.out.println(numbers[position]);
}

Example how to convert String to array of int

// Example input
String input = "1 2 3 4 5";

// Split elements by space
// So you receive array: {"1", "2", "3", "4", "5"}
String[] strings = input.split(" ");

// Create new array for "ints" (with same size!)
int[] number = new int[strings.length];

// Convert all of the "Strings" to "ints"
for (int position = 0; position < strings.length; position++) {
    number[position] = Integer.parseInt(strings[position]);
}

Upvotes: 1

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