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?

There's a straightforward solution to this, but before I begin: is there any reason that you're not just storing this as numbers from the get-go? — Makoto, Apr 10 '18 at 15:33
Check [this answer](https://stackoverflow.com/a/44909768/133203) then just attach an `allMatch` that checks whether they are numbers. — Federico klez Culloca, Apr 10 '18 at 15:35

vincrichaud · Accepted Answer · 2018-04-10T16:18:35.927

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

Paplusc · Answer 2 · 2018-04-10T15:49:32.970

0

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;
}

edited Apr 10 '18 at 15:49

answered Apr 10 '18 at 15:39

Paplusc

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Ok, but this is missing the part where you traverse the multidimensional array. – Federico klez Culloca Apr 10 '18 at 15:39
just go through the array with a loop – Paplusc Apr 10 '18 at 15:42
That won't work, traversing the array will give you arrays. Then you'd need to flatten it first (or do nested loops to check that your function always returns true), which is a whole lot different than your answer. That's what's missing, and it's an important part of the question. – Federico klez Culloca Apr 10 '18 at 15:43

How to check if a two dimensional Array contains only digits

2 Answers2