Get length and iterate through nested array

Question

I have an array of coordinates from JSON. It looks like this.

[ [ [ [ 18.446000, -33.921060 ], [ 18.446020, -33.923410 ], [ 18.444510, -33.923620 ], [ 18.443350, -33.923990 ], [ 18.443350, -33.924360 ], [ 18.443360, -33.924970 ], [ 18.443230, -33.924970 ]]]]

I cannot work out how to get the length of the inner set of values [Lat,Lng],[Lat,Lng]... so I can loop through them. In python I would do something like:

for value in values[0][0]:
    print value

What would the equivalent in java be? I think I am getting massively confused with arrays in Java. I'm trying to get at them using something like this at the moment, but to be honest I'm shooting in the dark here.

List<JSONObject> geocords = Arrays.asList(cords.getJSONObject(0))

I've tried things like:

for (i=0; HOW TO GET LENGTH OF INNER SET OF VALUES?; i++){

}

EDIT

List<JSONObject> geocords = Arrays.asList(cords.getJSONObject(0))

Throws a JSONException.

If I change it to:

List<JSONArray> geocords = Arrays.asList(cords.getJSONArray(0));

Then geocords outputs as:

[[[[18.49576,-34.01209],[18.49447,-34.01473],[18.49327,-34.01705],[18.48914,-34.02501],[18.48866,-34.02592],[18.48873,-34.02612],[18.48912,-34.027],[18.48917,-34.02711],[18.49,-34.02899],[18.49003,-34.02976],[18.49031,-34.03164],[18.49051,-34.03264],[18.49093,-34.03462],[18.49152,-34.03742],[18.4917,-34.03772],[18.4918,-34.03782],[18.49186,-34.038],[18.49184,-34.03823],[18.49159,-34.0388],[18.49105,-34.03986],[18.49041,-34.04115],[18.48984,-34.04113],[18.4891,-34.04246],[18.48784,-34.04214],[18.48791,-34.04326],[18.48786,-34.04356],[18.48754,-34.04391],[18.48738,-34.04391],[18.48713,-34.04399],[18.48693,-34.04405],[18.48677,-34.04407],[18.48665,-34.04396],[18.4865,-34.0439],[18.48631,-34.04396],[18.48611,-34.04408],[18.48598,-34.04427],[18.48599,-34.04456],[18.48595,-34.04487],[18.48583,-34.04508],[18.48557,-34.04531],[18.48527,-34.04543],[18.48496,-34.04547],[18.48446,-34.04553],[18.48418,-34.04498],[18.48342,-34.04371],[18.48335,-34.0436],[18.48267,-34.04247],[18.47827,-34.04429],[18.47818,-34.04436],[18.47645,-34.04146],[18.47652,-34.04122],[18.47662,-34.04039],[18.47632,-34.03942],[18.47611,-34.03916],[18.47611,-34.0391],[18.47589,-34.03756],[18.47588,-34.03748],[18.47438,-34.03715],[18.47389,-34.0368],[18.47308,-34.03643],[18.47103,-34.03727],[18.47053,-34.03757],[18.47029,-34.03773],[18.46953,-34.03846],[18.46925,-34.03861],[18.46915,-34.03867],[18.46899,-34.03872],[18.46877,-34.03879],[18.4683,-34.03884],[18.46806,-34.03887],[18.46791,-34.03889],[18.46757,-34.03897],[18.46747,-34.03906],[18.46728,-34.03925],[18.46711,-34.03945],[18.46698,-34.03967],[18.46685,-34.03992],[18.46672,-34.04016],[18.46664,-34.04102],[18.46656,-34.04251],[18.46648,-34.04292],[18.46637,-34.04356],[18.46617,-34.04355],[18.46585,-34.0435],[18.46575,-34.04348],[18.46561,-34.04346],[18.46538,-34.04342],[18.46515,-34.04339],[18.46484,-34.04334],[18.46447,-34.04328],[18.46396,-34.0432],[18.4636,-34.04314],[18.46366,-34.04288],[18.46374,-34.04253],[18.46237,-34.04232],[18.46158,-34.0422],[18.4613,-34.04216],[18.45996,-34.04196],[18.45925,-34.04185],[18.45863,-34.04176],[18.45756,-34.0416],[18.45656,-34.04144],[18.45602,-34.04136],[18.45571,-34.04131],[18.456,-34.03991],[18.45458,-34.03972],[18.45408,-34.03965],[18.45373,-34.03968],[18.45337,-34.03972],[18.45303,-34.03981],[18.45042,-34.0406],[18.45022,-34.04002],[18.45018,-34.03994],[18.45005,-34.03972],[18.44967,-34.03905],[18.44912,-34.03807],[18.44876,-34.03742],[18.44861,-34.03717],[18.44854,-34.03702],[18.44843,-34.03683],[18.44822,-34.03646],[18.44812,-34.03628],[18.44801,-34.0361],[18.44791,-34.0359],[18.44781,-34.03573],[18.4476,-34.03535],[18.44752,-34.03521],[18.44737,-34.03495],[18.44723,-34.03471],[18.44709,-34.03444],[18.44698,-34.03425],[18.44687,-34.03405],[18.44669,-34.03374],[18.44635,-34.03313],[18.44625,-34.03295],[18.44613,-34.03272],[18.446,-34.03251],[18.4459,-34.0323],[18.44576,-34.03205],[18.44516,-34.031],[18.44408,-34.029],[18.44385,-34.02882],[18.44376,-34.02921],[18.4437,-34.02938],[18.44364,-34.02947],[18.44328,-34.02994],[18.44296,-34.03014],[18.44236,-34.03017],[18.44179,-34.03008],[18.44168,-34.03007],[18.44054,-34.02989],[18.44019,-34.02988],[18.44001,-34.02992],[18.43968,-34.02999],[18.43951,-34.03006],[18.4394,-34.03012],[18.43935,-34.03017],[18.43849,-34.03086],[18.43808,-34.03122],[18.43759,-34.03164],[18.43714,-34.032],[18.43695,-34.03215],[18.43645,-34.03234],[18.43585,-34.03256],[18.43542,-34.03272],[18.43464,-34.033],[18.43413,-34.03319],[18.4336,-34.03335],[18.43299,-34.0335],[18.43272,-34.03353],[18.43235,-34.03358],[18.43147,-34.03363],[18.43134,-34.03364],[18.43102,-34.03367],[18.43065,-34.03373],[18.4299,-34.03394],[18.42951,-34.03404],[18.42911,-34.03414],[18.42893,-34.03415],[18.42873,-34.03418],[18.42845,-34.03422],[18.42816,-34.03429],[18.42647,-34.03472],[18.42627,-34.03478],[18.42608,-34.0349],[18.4248,-34.03586],[18.42294,-34.03728],[18.42202,-34.03798],[18.42184,-34.03806],[18.42168,-34.03813],[18.42137,-34.03811],[18.42104,-34.03806],[18.42068,-34.03799],[18.41975,-34.03781],[18.41935,-34.03786],[18.41911,-34

Can you post the result of System.out.println(geocords) ?

Suresh Atta
– Suresh Atta

2013-07-13 07:14:26 +00:00
Commented Jul 13, 2013 at 7:14 — Suresh Atta
– Suresh Atta, Commented Jul 13, 2013 at 7:14
Hi. Have updated as requested.

andrewtrench
– andrewtrench

2013-07-13 07:35:12 +00:00
Commented Jul 13, 2013 at 7:35 — andrewtrench
– andrewtrench, Commented Jul 13, 2013 at 7:35
What json library do you use?

Jirka
– Jirka

2013-07-13 08:12:11 +00:00
Commented Jul 13, 2013 at 8:12 — Jirka
– Jirka, Commented Jul 13, 2013 at 8:12
I'm using the org.json library

andrewtrench
– andrewtrench

2013-07-13 08:14:53 +00:00
Commented Jul 13, 2013 at 8:14 — andrewtrench
– andrewtrench, Commented Jul 13, 2013 at 8:14
Ok, I updated my code to use org.json library.

Jirka
– Jirka

2013-07-13 14:08:40 +00:00
Commented Jul 13, 2013 at 14:08 — Jirka
– Jirka, Commented Jul 13, 2013 at 14:08

Jirka · Accepted Answer · 2013-07-13 14:07:52Z

3

Are you sure the four square brackets at the beginning are ok? If yes, then this should work:

        // get the array of coordinates buried two levels down of singleton arrays  
        JSONArray array = coord.getJSONArray(0).getJSONArray(0);

        // iterate through the array of coordinates
        for (int i = 0; i < array.length(); i++) {
            JSONArray inside = array.getJSONArray(i);
            for (int j = 0; j < inside.length(); j++) {
                System.out.println(inside.getDouble(j));
            }
        }

I am not sure why json.org does not provide a more friendly interface (like iterable)

edited Jul 13, 2013 at 14:07

answered Jul 13, 2013 at 7:26

Jirka

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Comments

score 0 · Accepted Answer · 2013-07-13 07:26:43Z

0

You would loop through the inner set like so in Java:

for (int i=0;i<array.length;i+=1)
{
     for (int j=0;j<array[i].length;j+=1)
     {
          System.out.println(array[i][j]);
     }
}

Alternatively, i could be hardcoded to the index that you want to run through.

edited Jul 13, 2013 at 7:26

answered Jul 13, 2013 at 7:21

user2577094

1 Comment

andrewtrench Over a year ago

Hi. Thanks for the guidance. I have been trying something along these lines but get an error "The type of the expression must be an array type but it resolved to JSONArray"

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