Rekursive Summe von Array Elementen

Test.java

import java.util.Arrays;
import java.util.List;
public class Test {
	/**
	 * @author Ben Rexin <[email protected]
	 */
	public static void main(String[] args) {
		List<Integer> array = Arrays.asList(1,2,3,4);
		System.out.println(sum(array));
	}

	/**
	 * @author Ben Rexin <[email protected]
	 * @param list of Integer
	 * @return Integer
	 */
	public static Integer sum(List<Integer> list) { return sum(list,0,0); }
	/**
	 * @author Ben Rexin <[email protected]
	 * @param list of Integer
	 * @param index as position within list
	 * @param accu sum of elements in list from 0 to index 
	 * @return Integer
	 */
	public static Integer sum(List<Integer> list, Integer index, Integer accu) {
		if (list == null || index == null || accu == null) throw new IllegalArgumentException();
		return index == list.size() ? accu : sum(list, index +1, accu + list.get(index));
	}
}