import java.util.Collections;
import java.util.List;

import com.google.common.collect.Lists;
import com.google.common.primitives.Ints;

public class IntArray {

	public static int[] ofSize(int size) {
		if (size < 0) throw new IllegalArgumentException(
				String.format("Expected a size [%d] to be at least 0", size));
		List<Integer> ints = Lists.newArrayList();
		for (int n = 0; n < size; n++) ints.add(n);
		Collections.shuffle(ints);
		return Ints.toArray(ints);
	}
}

import java.util.Random;

import org.junit.Test;

public class IntArrayTest {

	@Test public void ofSizeIsRandom() {
		Random randomizer = new Random();
		int size = randomizer.nextInt(1000) + 2;
		int index1 = randomizer.nextInt(size), index2;
		do index2 = randomizer.nextInt(size); while (index1 == index2);
		int value1 = randomizer.nextInt(size), value2;
		do value2 = randomizer.nextInt(size); while (value1 == value2);
		int round = 1;
		do {
			int[] ints = IntArray.ofSize(size);
			if (ints[index1] == value1 && ints[index2] == value2) break;
			int threshold = size * (size - 1);
			if (round % threshold == 0) {
				System.out.println("perhaps the function does not produce random arrays");
			}
			round++;

		} while (true);
	}
}