Update OddOccurrencesInArray.java

[gunescelil]

make solution like this

// write your code in Java SE 8
HashSet dups = new HashSet<>();

    for (int i = 0; i < A.length; i++)
    {
        if (!dups.add(A[i]))
        {           
            dups.remove((A[i]));
        } 
    }
    
    return (Integer) dups.toArray()[0];