private static RandomTree randomTreeByBuilder(int minSize, int maxSize) {
assert minSize > 3;
ThreadLocalRandom random = ThreadLocalRandom.current();
BTree.Builder<Integer> builder = BTree.builder(naturalOrder());
int targetSize = random.nextInt(minSize, maxSize);
int maxModificationSize = (int) Math.sqrt(targetSize);
TreeSet<Integer> canonical = new TreeSet<>();
int curSize = 0;
TreeSet<Integer> ordered = new TreeSet<>();
List<Integer> shuffled = new ArrayList<>();
while (curSize < targetSize) {
int nextSize = maxModificationSize <= 1 ? 1 : random.nextInt(1, maxModificationSize);
// leave a random selection of previous values
(random.nextBoolean() ? ordered.headSet(random.nextInt()) : ordered.tailSet(random.nextInt()))
.clear();
shuffled =
new ArrayList<>(
shuffled.subList(0, shuffled.size() < 2 ? 0 : random.nextInt(shuffled.size() / 2)));
for (int i = 0; i < nextSize; i++) {
Integer next = random.nextInt();
ordered.add(next);
shuffled.add(next);
canonical.add(next);
}
switch (random.nextInt(5)) {
case 0:
builder.addAll(ordered);
break;
case 1:
builder.addAll(BTreeSet.of(ordered));
break;
case 2:
for (Integer i : ordered) builder.add(i);
case 3:
builder.addAll(shuffled);
break;
case 4:
for (Integer i : shuffled) builder.add(i);
}
curSize += nextSize;
maxModificationSize = Math.min(maxModificationSize, targetSize - curSize);
}
BTreeSet<Integer> btree = BTreeSet.<Integer>wrap(builder.build(), naturalOrder());
Assert.assertEquals(canonical.size(), btree.size());
return new RandomTree(canonical, btree);
}
protected Builder(Comparator<? super V> comparator) {
builder = BTree.builder(comparator);
}