java question help please

Write an iterator that takes an lterable in the constructor and the sequence it produces is every pair of elements added together. Add the last element with 0 if you run out of pairs. e.g., input: 2, 5, 3, 7 rightarrow produces 7, 10 input: 1, 2, 3, 4, 5, 6, 7 rightarrow produces 3, 7, 11, 7