Is there anything like Enumerable.Range(x,y) in Java?

Question

Is there something like C#/.NET's

IEnumerable<int> range = Enumerable.Range(0, 100); //.NET

in Java?

Answer 1

As Java 8, this is possible with java.util.stream.IntStream.range(int startInclusive, int endExclusive)

Before Java8:

There is not such thing in Java but you can have something like this:

import java.util.Iterator;

public class Range implements Iterable<Integer> {
    private int min;
    private int count;

    public Range(int min, int count) {
        this.min = min;
        this.count = count;
    }

    public Iterator<Integer> iterator() {
        return new Iterator<Integer>() {
            private int cur = min;
            private int count = Range.this.count;
            public boolean hasNext() {
                return count != 0;
            }

            public Integer next() {
                count--;
                return cur++; // first return the cur, then increase it.
            }

            public void remove() {
                throw new UnsupportedOperationException();
            }
        };
    }
}

For example you can use Range by this way:

public class TestRange {

    public static void main(String[] args) {
        for (int i : new Range(1, 10)) {
            System.out.println(i);
        }
    }

}

Also if you don't like use new Range(1, 10) directly, you can use factory class for it:

public final class RangeFactory {
    public static Iterable<Integer> range(int a, int b) {
        return new Range(a, b);
    }
}

And here is our factory test:

public class TestRangeFactory {

    public static void main(String[] args) {
        for (int i : RangeFactory.range(1, 10)) {
            System.out.println(i);
        }
    }

}