Iterators - in COBOL and Java

$set ilusing(System.Collections.Generic)

class-id Iterators.

method-id Use static.

    perform varying i as binary-long thru GetSequence()
        display i
    end-perform


    declare #instance = new Iterators()
    perform varying i as binary-long thru #instance
        display i
    end-perform
end method.


iterator-id GetSequence static yielding retn as binary-long.
    declare c as binary-long = 1
    perform until exit
        add 1 to c

        *> yield the next number
        set retn to c
        goback

        if c < 5
            *> yield the next number
            set retn to c * 10
            goback
        else
            *> end the iterator
            exit iterator
        end-if
    end-perform
end iterator.


*> Define an iterator for the current class
iterator-id self yielding retn as binary-long.
    perform varying i as binary-long from 23 by -5 until i < 0
        set retn to i
        goback
    end-perform
end iterator.
end class.

// Java does not support coroutines so iterators can only be implemented
// as classes that implement java.util.Iterator.

import java.util.Iterator;

class iterators implements Iterable<Integer>
{
    public static void Use()
    {
        for (Iterator seq = new GetSequence(); seq.hasNext(); )
        {
            System.out.println(seq.next());
        }

        iterators instance = new iterators();
        for (int i : instance)
        {
            System.out.println(i);
        }
    }

    static class GetSequence implements Iterator<Integer> {
        private boolean nextIsMultiplied = false;
        private int c = 1;

        public boolean hasNext() {
            return c < 5;
        }

        public Integer next() {
            if (!nextIsMultiplied) {
                nextIsMultiplied = true;
                // yield the next number
                c++;
                return c;
            } else {
                nextIsMultiplied = false;
                // yield the next number
                return c * 10;
            }
        }
    }

    // Define an iterator for the current class
    public Iterator<Integer> iterator() {
        return new GetOtherIterator();
    }

    // Our iterator class that is created when iterating this instance
    static class GetOtherIterator implements Iterator<Integer> {
        private int i = 23;

        public boolean hasNext() {
            return i >= 0;
        }

        public Integer next() {
            int result = i;
            i -= 5;
            return result;
        }
    }
}