Sum a list of objects based on BigDecimal field in single line

Question

Suppose we have:

class Foo {
   public BigDecimal field;
}

and that we have a list of Foo instances, i.e. List<Foo> list.

How can we calculate the sum of the values of the field from the objects in the list in a single line?

I found examples of similar cases using streams but they handle simpler cases and do not work for this; such as calculating for List<Integer> or when the field is something easily "summable" (int, Integer...).

score 2 · Accepted Answer · edited Feb 18 '20 at 16:10

2

list.stream().map(foo -> foo.field).reduce(BigDecimal.ZERO, (a, b) -> a.add(b));

edited Feb 18 '20 at 16:10

Caner

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answered Feb 18 '20 at 15:56

Horatiu Jeflea

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doesnt work, you cannnot add `Foo` objects – Caner Feb 18 '20 at 15:57
1

`.map(Foo::getField).reduce(BigDecial::add).orElse(BigDecimal.ZERO)`, but this was asked _so many_ times already. – Eugene Feb 18 '20 at 15:57
@Eugene `Foo` has no "getField" method – Caner Feb 18 '20 at 16:02
@Caner how do you access `field` then? – Eugene Feb 18 '20 at 16:03
it's a public field – Caner Feb 18 '20 at 16:04
1

@Caner the answer of Horatiu Jeflea should work. Are you sure you copied it right? – KunLun Feb 18 '20 at 16:06
the answer got an update...now it works – Caner Feb 18 '20 at 16:09

Sum a list of objects based on BigDecimal field in single line

1 Answers1