Thanks, investigating.

Does not break the unit tests. A bit difficult to isolate the functional change due to all of the style updates. In XML.toString(), Array values found in a JSONObject are converted into JSONArray instances:

New functionality:
XML.toString()
Insert at line 409 of the original code:

} else if (value.getClass().isArray()) {
    value = new JSONArray(value);
}

New behavior:

• When processing JSONObject values, convert Array to JSONArray.

Unrelated note:
Don't think line 410 of the original code does anything, due to the return on line 466.

            string = value instanceof String ? (String)value : null;

Seems like a good enhancement, but needs more study of how the behavior is changed.

I agree with you about line 410. I think that would be outside the scope of this PR though, unless you want me to include it.

What problem does this code solve?
XML.toString() does not work as expected when a JSONObject contains Array type values. This results inconsistent handling between raw JSON, JSONArray values and Array values.

Changes to the API?
No.

Changes to how the code behaves?
When processing JSONObject values, Arrays will be converted to JSONArrays before
further processing.
Example

{
    "arr" : [
        "One",
        [
             "Two",
             "Three"
        ],
         "Four",
         []
     ]
}

Produces this XML from raw JSON or internal JSONArrays (correct):

    <arr>One</arr>
    <arr>
        <array>Two</array>
        <array>Three</array>
    </arr>
    <arr>Four</arr>
    <arr></arr>

Currently produces this XML from internal arrays (incorrect):

    <arr>One</arr>
    <arr>Two</arr>
    <arr>Three</arr>
    <arr>Four</arr>

The code fix will bring the Array value in sync with raw JSON and JSONArray.

Does it break the unit tests?
The unit tests will be updated. See stleary/JSON-Java-unit-test#29.

Will this require a new release?
No, this change will be rolled into the next release.

Should the documentation be updated?
No, this is an internal change.