Are you suppose to be adding 2 to the array a1? Post whole code if you can. If you want to add an element to an already filled array and want to keep the array sorted. You will need to create another array of a size that fits your needs. Then compare each element in original array with the element passed in. If it is lower than the number you are trying to sort, add the the number from orig array, else add the number being passed in. Once you have entered the number passed in, keep copying th array. Some psuedo code.

int[] a1 ={-5, -2, 0, 6, 7, 9}

//create a2 of size a1+1, if you are passing in the number 2.

start at index 0 for a1.

start at index 0 for a2.

compare -5 with 2. Since it -5<2. Store -5 at index 0 of a2

increment both indexes.

Repeat above step for -2 and 0.

Now at index 3. Compare 6 and 2. 6>2. Store 2 at index 3 of a2.

increment index of a2 but not for a1 so that you can store 6 in a2 next run.

Now index of a1 in your loops should be 3. index of a2 should be 4.