Deserializing json array using gson

Question

Continuing from this question.

I\'m having trouble deserializing the following json array (Sorry for the size):

\"geometry\": { \"type\": \"Polygon\"         


        

Answer 1

The coordinates in JSON is a three-dimensional matrix. With Collection[][] you're going one dimension too far. The Collection itself is already one dimension, so you've basically declared a four-dimensional matrix.

With the error message, Gson is basically telling you that it is expecting an object for the fourth dimension, but it instead encountered a double.

The following represent valid three-dimensional matrices which should be perfectly handled by Gson:

• private double[][][] coordinates; (recommended)
• private Collection[] coordinates;
• private Collection coordinates;
• private Collection> coordinates;
• private Collection>> coordinates;

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That said, I would prefer List above Collection in this particular case. With a List you can guarantee that it's been filled with insertion order and you'll be able to get elements by index.