How to check if a two dimensional Array contains only digits

Question

I got a two dimensional String array with only numbers in it;

System.out.println(Arrays.deepToString(temp));
[[1, 3, 1, 2], [2, 3, 2, 2], [5, 6, 7, 1], [3, 3, 1, 1]]

I need to check if the array contains only numbers, otherwise I will throw an exception.

System.out.println(Arrays.deepToString(temp[0]).matches("[0-9]*")); - return false                           
System.out.println(Arrays.deepToString(temp[0]).matches("[0-9]+")); - return false

As far as I get, The code says that the array does not contains only numbers, because when converted to char the array is like :

[[, [, 1, ,,  , 3, ,,  , 1, ,,  , 2, ], ,,  , [, 2, ,,  , 3, ,,  , 2, ,,  , 2, ], ,,  , [, 5, ,,  , 6, ,,  , 7, ,,  , 1, ], ,,  , [, 3, ,,  , 3, ,,  , 1, ,,  , 1, ], ]]

How can I check if it contains only numbers?

Answer 1

You should first loop through your array. Since each element will be an array, loop through it. Then for each element (that should be a String) check if it's what you want.

To loop through your Array of arrays :

boolean arrayIsCorrect = true; //flag to know if array is correct
for(int i=0; i<array.length; i++) { //loop through the array of arrays
    for(int j=0; j<array[i].length; j++) { //loop through the sub-array array[i]
        if(!isCorrect(array[i][j])) {
            arrayIsCorrect = false;
            break; //optimization not required
        }
    }
    if(!arrayIsCorrect) { //optimization not required
        break;
    }
}
System.out.println("Is the array correct ? " + arrayIsCorrect ); //print the result

In your question it's not clear if you want elements to be digit or numbers. In case of digit the function isCorrect() should look like :

public boolean isCorrect(String s) {
    return s.matches("[0-9]");
}

In case of number, check this answer

Answer 2

I would make a function that checks if it is numeric.

Something like this:

for(int i = 0; i < array.size();i++){
    for(int j = 0; j < array.size();j++){
        if(temp.isNumeric(temp[i][j] == false)
        break;
    }
}

public static boolean isNumeric(String value) {
    boolean result;
    try {
        Integer.parseInt(value);
        result = true;
    } catch (NumberFormatException excepcion) {
        result = false;
    }
    return result;
}