Get element from JSON file using getJSONArray() and getJSONObject() in Java

Question

I would like to walk through the json file below and save the part after "coordinates".

The json file:

{"type": "FeatureCollection","features": [{"type": "Feature","properties": {},"geometry": {"type": "LineString","coordinates": [[4.354282,52.032195],[4.354087,52.032462],[4.353783,52.032962],[4.353579,52.033437],[4.353333,52.034151],[4.352991,52.03545],[4.352517,52.037002],[4.352442,52.037352],[4.352368,52.0378],[4.352336,52.038238],[4.352331,52.039962],[4.352346,52.040706]
    ]
  }
}

] }

I've seen code using getJSONArray() and getJSONObject() here and here. This information helped me to select (in my case) the "geometry" tree.

My code so far (test2.geojson is the json file mentioned above):

        String output = new String(Files.readAllBytes(Paths
                .get("C:\\Users\\****\\Desktop\\test2.geojson")));

        JSONObject obj = new JSONObject(output);

        JSONArray jsonArray = obj.getJSONArray("features");
        System.out.println(jsonArray);

However, this only rearranges the file and appends the first part to the end of the file.

[{"geometry":{"coordinates":[[4.354282,52.032195],[4.354087,52.032462],[4.353783,52.032962],[4.353579,52.033437],[4.353333,52.034151],[4.352991,52.03545],[4.352517,52.037002],[4.352442,52.037352],[4.352368,52.0378],[4.352336,52.038238],[4.352331,52.039962],[4.352346,52.040706]],"type":"LineString"},"type":"Feature","properties":{}}]

Any solutions to get the desired output of:

[[4.354282,52.032195],[4.354087,52.032462],[4.353783,52.032962],[4.353579,52.033437],[4.353333,52.034151],[4.352991,52.03545],[4.352517,52.037002],[4.352442,52.037352],[4.352368,52.0378],[4.352336,52.038238],[4.352331,52.039962],[4.352346,52.040706]
    ]
  }
}

] }

Thanks in advance. Cheers!

Nicholas Ng · Accepted Answer · 2015-06-25 01:42:17Z

2

As "geometry" is a json object {}, "coordinates" is a json array [],

You should be doing

JSONArray jsonArray = obj.getJSONArray("features");
JSONArray resultArray = jsonArray.getJSONObject[0].getJSONObject("geometry").getJSONArray("coordinates")

edited Jun 25, 2015 at 1:42

answered Jun 24, 2015 at 14:08

Nicholas Ng

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6 Comments

Camelaria Over a year ago

jsonArray.getJSONObject("geometry") gives the following error. The method getJSONObject(int) in the type JSONArray is not applicable for the arguments (String). I'm using the org.json library.

Nicholas Ng Over a year ago

get the first object from jsonArray first, then apply my code

Camelaria Over a year ago

Thanks for helping. jsonArray.getJSONArray[0] is throwing: getJSONArray cannot be resolved or is not a field.

Camelaria Over a year ago

Are you also using org.json library? Just to be sure.

Nicholas Ng Over a year ago

@Camelaria ops, you should be using jsonArray.getJSONObject(0) ....instead of jsonArray.getJSONArray(0)...my bad but hey you can spot this easily too~

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