Here you can find the source of getLongListSum(Collection
public static Long getLongListSum(Collection<Long> c)
//package com.java2s; import java.util.Collection; public class Main { public static Long getLongListSum(Collection<Long> c) { Long sum = 0l;//from w w w . j a v a 2 s. c om for (Long i : c) { sum += i; } return sum; } }