Write a recursive Java method knapsack that takes a list of allowed integer numbers and a target sum and prints all of the possible choices of numbers that sum to the target. Assume the numbers are all positive.

For example, if list were [1, 2, 3, 5], then knapsack(list, 3) would output:

[1, 1, 1]

[1, 2]

[2, 1]

[3]

Do not make changes to the list of numbers.