Javadoc
Accumulate values under a key. It is similar to the put method except
that if there is already an object stored under the key then a
JSONArray is stored under the key to hold all of the accumulated values.
If there is already a JSONArray, then the new value is appended to it.
In contrast, the put method replaces the previous value.
If only one value is accumulated that is not a JSONArray, then the
result will be the same as using put. But if multiple values are
accumulated, then the result will be like append.