public static int positive(final int value) {
		if (value <= 0) {
			throw new IllegalArgumentException(format(
				"Value is not positive: %d", value
			));
		}
		return value;
	}
Require the given {@code value} to be positive (&gt; 0).
@param value the value to check
@return the given value
@throws IllegalArgumentException if the given {@code value} is smaller than
        or equal zero.
jenetics/src/main/java/io/jenetics/internal/util/Requires.java