Is there any method in Java to init a set by step 1 or other length?

Question

For example, I like to init a set like [1,2,3, ...,100].

Usually, we do as follows:

for(int i = 1;i <= 100;i++ ){
    set.add(i);
}

Is there any method to do this more conveniently?

Such as someMethod(startIndex, endIndex, step);

By using that, we can easily init a set like [1,2,3,4,5] or [1,3,5,7,9] or others.

Answer 1

You can use Java 8 Streams.

For example :

Set<Integer> mySet = IntStream.range(1,101).boxed().collect(Collectors.toSet());

or for odd numbers only :

Set<Integer> mySet = IntStream.range(1,101).filter(i->i%2==1).boxed().collect(Collectors.toSet());

• IntStream.range is an easy way to obtains numbers in a given range.
• Then you can apply filters if you only want some of the numbers.
• Finally you can collect them to any collection you wish.