dealing with garbage value in merge sort

dealing with garbage value in merge sort

we have two sorted arrays and have to merge those arrays into a third one,
yeah that's easy,
int[] answer = new int[a.length + b.length];
int i = 0, j = 0, k = 0;
while (i < a.length && j < b.length)
{
if (a[i] < b[j])
{
answer[k] = a[i];
i++;
}
else
{
answer[k] = b[j];
j++;
}
k++;
}
while (i < a.length)
{
answer[k] = a[i];
i++;
k++;
}
while (j < b.length)
{
answer[k] = b[j];
j++;
k++;
}
return answer;
}
but if a[] finds a garbage value at a[a.length+1] and b[] finds garbage at
b[b.length] and let both garbage values are not in sorted order, so, how
can we avoid those?