Java: Equivalent of Python's range(int, int)?

Question

Does Java have an equivalent to Python\'s range(int, int) method?

Answer 1

Groovy's nifty Range class can be used from Java, though it's certainly not as groovy.

Answer 2

Java 8

private static int[] range(int start, int stop, int step) {
    int[] result = new int[(stop-start)%step == 0 ? (stop-start)/step : (stop-start)/step+1];
    int count = 0;
    Function<Integer, Boolean> condition = step > 0 ? (x) -> x < stop : (x) -> x > stop;
    for (int i = start; condition.apply(i); i += step) {
        result[count] = i;
        count++;
    }
    return result;
}

Answer 3

You can use the following code snippet in order to get a range set of integers:

    Set<Integer> iset = IntStream.rangeClosed(1, 5).boxed().collect
            (Collectors.toSet());

Answer 4

Guava also provides something similar to Python's range:

Range.closed(1, 5).asSet(DiscreteDomains.integers());

You can also implement a fairly simple iterator to do the same sort of thing using Guava's AbstractIterator:

return new AbstractIterator<Integer>() {
  int next = getStart();

  @Override protected Integer computeNext() {
    if (isBeyondEnd(next)) {
      return endOfData();
    }
    Integer result = next;
    next = next + getStep();
    return result;
  }
};

Answer 5

Java 9 - IntStream::iterate

Since Java 9 you can use IntStream::iterate and you can even customize the step. For example if you want int array :

public static int[] getInRange(final int min, final int max, final int step) {
    return IntStream.iterate(min, i -> i < max, i -> i + step)
            .toArray();
}

or List :

public static List<Integer> getInRange(final int min, final int max, final int step) {
    return IntStream.iterate(min, i -> i < max, i -> i + step)
            .boxed()
            .collect(Collectors.toList());
}

And then use it :

int[] range = getInRange(0, 10, 1);

Answer 6

public int[] range(int start, int length) {
    int[] range = new int[length - start + 1];
    for (int i = start; i <= length; i++) {
        range[i - start] = i;
    }
    return range;
}

(Long answer just to say "No")