Create a List of random Integers using Stream and sum all elements except the smallest?

user_14752499 0
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I want to generate 4 random numbers, ranging from 1 through 6 inclusive. Then I want to get the sum of these elements excluding the smallest value.

I am currently creating one stream to populate a list:

List<Integer> values =  r.ints(4,1,7).boxed().collect(Collectors.toList())

Then I remove the smallest value and use another stream to get the sum of the values:

values.stream().mapToInt(Integer::intValue).sum();

Can someone suggest a way to perform all these operations in a single stream?

java-stream java
2 Answers

Sort the stream, then skip the first (ie smallest) element:

int sumExceptSmallest = IntStream.of(4,1,7).sorted().skip(1).sum(); // 11

or in your specific case:

int sumExceptSmallest = r.ints(4,1,7).sorted().skip(1).sum();

Note that while this may be the coolest and most efficient for the coder, it is not the most efficient possible solution because the sort has time complexity of O(n log n). The most efficient run time would be a single pass to both find the smallest and compute the sum, then subtract one from the other, yielding the solution in O(n) time.

user_2561960

Using IntSummaryStatistics can calculate this in your stream with a single pass:

IntStream stream = /* random stream of integers */;
IntSummaryStatistics stats = stream.summaryStatistics();
int sum = stats.sum();
sum -= stats.min(); //sum, minus the lowest element
user_17860650
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