Java: How to implement the following quicksort algorithm in java, and test it with "input_100.txt"??

Any help will be appreciated!

QuickSort (A, p, r)

if p < r

q = Partition (A, p, r)

QuickSort( A, p, q-1)

QuickSort( A, q+1, r)

Partition (A, p, r)

x = A [r]

i = p-1

for j = p to r-1

if A[j] <= x

i = i+1

exchange A[i] with A[j]

exchange A [i +1] with A[r]

return i+1