I get the java.lang.NullPointerException and i don't understand why

public class Array
{
    public int dimensione;
    public int[] arr;
    
    /*
     * n: array dimension
     */
    public Array(int n)
    {
        dimensione = n;
        int max = 10;
        int min = 1;
        
        int[] arr = new int[n];
        
        //put random number between 1 and 10 in the array
        for(int i = 0; i < n; i++)
        {
            arr[i] = (int)(Math.random() * ((max - min) + 1) + min);
        }
    }
    
    public String toString()
    {
        String arrayToString = "";
        
        for(int i = 0; i < dimensione; i++)
        {
            arrayToString = arrayToString + arr[i] + " ";
        }
        
        return arrayToString;
    }
}

I have this code and i get the error but i don’t understand why. Is the array not being filled correctly and it stays null so when i try to write it as a string it finds a null array? if yes, why is not working? how do i solve it?

>Solution :

In the constructor, you declare a local variable arr which shadows the class’s arr field, which remains null. That causes a NullPointerException when you call toString (which you apparently do somewhere).

Change

int[] arr = new int[n];

to

arr = new int[n];