refactor: use isEmpty to make intention clear

[zielint0]

No description provided.

[pvojtechovsky]

I personally prefer positive size() > 0. so it is ok for me like it is now. If others thinks that !isEmpty() is better, them I can live with that too :-)

[zielint0]

I have fixed previous defects like this.
This PR fixes some new ones.

[monperrus]

size() > 0 is slightly more explicit (you don't have to know the meaning and contracts of isEmpty).

If Pavel prefers it, let's keep it.

Thanks @zielint0 for the proposal.

[zielint0]

@pvojtechovsky
@monperrus
@surli

I fixed a lot of them in:
#2362
#2348
#2328
#2282

These are the last ones to fix.
It was merged by @surli so I think that this is useful.

Please consider reopening this pull request.

[zielint0]

@monperrus
To make reviewers life easy, I created a list of merged PRs.
If you want to see rationale or fact if something similar was merged or not, please take a look:
#2105

[pvojtechovsky]

I checked #2362 #2348 #2328 #2282 and I agree that it is more readable only in this case:

		if (splitRange.length == 1 || splitRange[1].length() == 0) {
change to
		if (splitRange.length == 1 || splitRange[1].isEmpty()) {

because it is positive expression: "If empty then do something", but in all other cases I need more time to understand new expressions, because they often contain negative condition. E.g.
if (!clone.getBody().getStatements().isEmpty()) { is not better then before

and the worst case is:

		assertTrue(factory.Type().getAll().size() > 0);
changed to
 		assertFalse(factory.Type().getAll().isEmpty());

Before I read it like "Type getAll contains something". Now I have to read: "It is not true that type get all is empty". My mind needs three time more effort to understand that ...
So I would not merge these other PRs.
Tomasz I very appreciate your cleaning effort, but in this particular case, I would not agree with these changes.

[monperrus]

reopened per @zielint0 's request in #2475

[zielint0]

@monperrus
Mercii!

@pvojtechovsky
Thank you for this explanation. I will rework it! :-)