Lambda expressions in Java 8

I want to use a lambda expression instead of a for loop to generate a list of numbers

So let's want to generate a list of all triangle numbers below 100 Trigonometry is the number of the following formula: (n * n) / 2

What is the best way to do this? At present, I have this:

Stream.iterate(1,n -> n + 1).limit(100)
            .map(n -> (n * n + n) / 2)
            .filter(a -> a < 100)
            .map(a -> a + "")
            .collect(Collectors.joining(",","Numbers: ","."));

But this seems unnecessarily over - calculated I iterate over n from 1 to 100 (because assuming I don't know what the maximum value of n is), then I map the trigonometric function of the list, and then I check which numbers are below 100. Is there a more effective way to do this? In addition, I can use the iterate function of stream to generate triangular numbers instead of iterate, limit, and then map?

Editor: so the point here is: once one of the triangle numbers exceeds 100, how does the calculation of a number stop? I usually write this:

ArrayList<Integer> triangles = new ArrayList<>(); 
for (int n=1;true;n++) {
    int num = (n*n+n)/2;

    if (num>100) break;

    triangles.add(num);
}

Once the triangle number exceeds 100, it stops, which is very effective; How do I preserve this efficiency in lambda expressions?

Solution

In general, what you are looking for is a period of time