Java8: sum values from specific field of the objects in a list

You can do

int sum = lst.stream().filter(o -> o.getField() > 10).mapToInt(o -> o.getField()).sum();

or (using Method reference)

int sum = lst.stream().filter(o -> o.getField() > 10).mapToInt(Obj::getField).sum();

You can try

int sum = list.stream().filter(o->o.field>10).mapToInt(o->o.field).sum();

Like explained here

You can also collect with an appropriate summing collector like Collectors#summingInt(ToIntFunction)

Returns a Collector that produces the sum of a integer-valued function applied to the input elements. If no elements are present, the result is 0.

For example

Stream<Obj> filtered = list.stream().filter(o -> o.field > 10);
int sum = filtered.collect(Collectors.summingInt(o -> o.field));