Accumulator.java

/*
 * Author: Piotr Likus, SpaceInSoft, 2015
 * License: MIT
 */
package com.spaceinsoft.utils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Generic number accumulator class.
 * Calculates sum of values, can be used with any built-in numeric type.
 * 
 * @author Piotr Likus
 */
public class Accumulator<T extends Number> {

    private T value;

    public Accumulator(T initValue) {
        value = initValue;
    }

    public void add(T aValue) {
        this.value = (T) NumberOperatorUtils.add(value, aValue);
    }

    public void addAll(List<T> list) {
        for (T item : list) {
            this.value = (T) NumberOperatorUtils.add(value, item);
        }
    }

    public T get() {
        return this.value;
    }

    public static void main(String[] args) {
        List<Integer> list = Arrays.asList(1, 3, 5);
        Accumulator<Integer> acc = new Accumulator<>(0);
        acc.addAll(list);
        acc.add(5);
        assert acc.get() == 14;
        System.out.println("Sum of integers: " + acc.get().toString());

        List<Double> dblList = Arrays.asList(1.7, 3.0, 5.1);
        Accumulator<Double> dblAcc = new Accumulator<>(0.0);
        dblAcc.addAll(dblList);
        dblAcc.add(3.3);
        System.out.println("Sum of doubles: " + dblAcc.get().toString());
    }
}

Output:

Sum of integers: 14
Sum of doubles: 13.100000000000001