Java re-engineering of two classes

It is asked to re-engineering this two Java classes in order to avoid code duplication and improve maintainability.

public class Adder {
  public int sum(int[] array) {
    int result = 0;
    for (int i = 0; i < array.length; i++) {
      result += array[i];
    }
  return result;
}

public class Multiplier {
  public int multiply(int[] array) {
    int result = 1;
    for (int i = 0; i < array.length; i++) {
      result *= array[i];
    }
  return result;
}

Pay attention to different result initialization; it's my main problem.