You can simply assign null to the reference. (This will work for any type of array, not just ints)
int[] arr = new int[]{1, 2, 3, 4};
arr = null;
This will 'clear out' the array. You can also assign a new array to that reference if you like:
int[] arr = new int[]{1, 2, 3, 4};
arr = new int[]{6, 7, 8, 9};
If you are worried about memory leaks, don't be. The garbage collector will clean up any references left by the array.
Another example:
float[] arr = ;// some array that you want to clear
arr = new float[arr.length];
This will create a new float[] initialized to the default value for float.