CODEWITHSUNDEEP
java
Vidya vid
Vidya vid

Reputation: 9

How to apply filter in sum function in java stream

I'm trying to apply a filter in the sum function. 

Integer lyf = events.stream().mapToInteger(i -> i).filter(sum()>100?100:sum());

but I'm facing an error.

Upvotes: 0

Views: 770

Answers (3)

lczapski
lczapski

Reputation: 4120

You can also do filtering and adding in steam with reduce:

Integer lyf = events.stream().reduce(0, (acc, v) -> acc > 100 ? 100 : (acc + v));

Other approach with short circuit to stop when sum > 100 is reached:

AtomicInteger acc = new AtomicInteger(0);
events.stream()
    .allMatch(x ->
        acc.updateAndGet((a) -> Math.min(100, (a + x) )) < 100
    );
Integer lyf = acc.get();

Upvotes: 0

Vikas
Vikas

Reputation: 7165

You need to first calculate the sum,

int sum = events.stream().mapToInt(i -> i).sum();
lyf = sum>100 ? 100 : sum;

Update: If you want to short circuit the Stream pipeline once a partial sum > 100 is reached, you can use a filter as below,

AtomicInteger sum = new AtomicInteger(0);
events.stream()
        .mapToInt(sum::addAndGet)
        .filter(i -> sum.get() > 100)
        .mapToObj(i1 -> {
            if (sum.get() < 100)
                return sum.get();
            else
                sum.set(100);
            return sum;
        })
        .findAny();
System.out.println(sum.get());

Upvotes: 1

Ahmed Sayed
Ahmed Sayed

Reputation: 1554

You will need to use one of the short-circuiting functions of the Stream. In this case I would use the allMatch() function.

Here's a small test I wrote to verify

@Test
public void testShortCircuitingSum() {
   final AtomicInteger totalSum = new AtomicInteger(0);
   IntStream.range(0, 1000).allMatch(value -> totalSumLessThan100(totalSum, value));
   System.out.println("Final sum is " + totalSum.get());
}

private static boolean totalSumLessThan100(AtomicInteger totalSum, int value) {
   if (totalSum.addAndGet(value) <= 100) {
      return true;
   }
   System.out.println("Total sum is " + totalSum.get() + ". Short-Circuiting at value " + value);
   System.out.println("Setting the value to 100");
   totalSum.set(100);
   return false;
}

Which prints

Total sum is 105. Short-Circuiting at value 14
Setting the value to 100
Final sum is 100

Upvotes: 0

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