Sum all the elements java arraylist

Question

If I had: ArrayList m = new ArrayList(); with the double values ​​inside, how should I do to add up all the ArrayList elements?

Answer 1

Java 8+ version for Integer, Long, Double and Float

    List ints = Arrays.asList(1, 2, 3, 4, 5);
    List longs = Arrays.asList(1L, 2L, 3L, 4L, 5L);
    List doubles = Arrays.asList(1.2d, 2.3d, 3.0d, 4.0d, 5.0d);
    List floats = Arrays.asList(1.3f, 2.2f, 3.0f, 4.0f, 5.0f);

    long intSum = ints.stream()
            .mapToLong(Integer::longValue)
            .sum();

    long longSum = longs.stream()
            .mapToLong(Long::longValue)
            .sum();

    double doublesSum = doubles.stream()
            .mapToDouble(Double::doubleValue)
            .sum();

    double floatsSum = floats.stream()
            .mapToDouble(Float::doubleValue)
            .sum();

    System.out.println(String.format(
            "Integers: %s, Longs: %s, Doubles: %s, Floats: %s",
            intSum, longSum, doublesSum, floatsSum));

15, 15, 15.5, 15.5