up vote 2 down vote favorite

I receive some data as a JSON response from a server. I extract the data I need and I want to put this data into a string array. I do not know the size of the data, so I cannot declare the array as static. I declare a dynamic string array:

String[] xCoords = {};

After this I insert the data in the array:

   for (int i=0; i<jArray.length(); i++) {
         JSONObject json_data = jArray.getJSONObject(i);
         xCoords[i] = json_data.getString("xCoord");
   }

But I receive the 

java.lang.ArrayIndexOutOfBoundsException
Caused by: java.lang.ArrayIndexOutOfBoundsException

What is the way to dynamically insert strings into a string array?

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2 Answers

up vote 6 down vote accepted

Use ArrayList although it is not really needed but just learn it:

ArrayList<String> stringArrayList = new ArrayList<String>();

   for (int i=0; i<jArray.length(); i++) {
         JSONObject json_data = jArray.getJSONObject(i);
         stringArrayList.add(json_data.getString("xCoord")); //add to arraylist
   }

//if you want your array
String [] stringArray = stringArrayList.toArray(new String[stringArrayList.size()]);
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I tried with this also, but if I type only String [] xCoords = xCoordsList.toArray(); it gives me a Type mismatch: cannot convert from Object[] to String[], so I make the line to String [] xCoords = (String[]) xCoordsList.toArray(); but this afterwards shows an 08-04 11:54:24.462: ERROR/AndroidRuntime(1173): Caused by: java.lang.ClassCastException: [Ljava.lang.Object; error. – Stefan Doychev Aug 4 '11 at 8:56
sorry I edited the answer .. just add String cast to the last statement`(String[]) ` – Sherif elKhatib Aug 4 '11 at 9:03
This was my point - even with the edited version the application stops (you have to Force close it) and the LogCat shows a java.lang.ClassCastException: [Ljava.lang.Object; Caused by: java.lang.ClassCastException: [Ljava.lang.Object; – Stefan Doychev Aug 4 '11 at 9:13
Are you sure you are not using ngArrayList.add(json_data);?? You must use ngArrayList.add(json_data.getString("xCoord")); I do not think you are using my code – Sherif elKhatib Aug 4 '11 at 9:35
Yes, sure about that - here is my code: ArrayList<String> xCoordsArrayList = new ArrayList<String>(); String[] xCoords = {}; JSONArray jArray = new JSONArray(result); for (int i=0; i<jArray.length(); i++) { JSONObject json_data = jArray.getJSONObject(i); xCoordsArrayList.add(json_data.getString("xCoord")); } xCoords = (String[]) xCoordsArrayList.toArray(); – Stefan Doychev Aug 4 '11 at 9:57
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up vote 3 down vote

Try like this

 String stringArray[];        
 stringArray=new String[jArray.length()];
 String xCoords[]=new String[jArray.length()];;

       for (int i=0; i<jArray.length(); i++) {
             JSONObject json_data = jArray.getJSONObject(i);
             xCoords[i] = json_data.getString("xCoord");
       }
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This works when inserting but when I try to extract the data from it with for (int i=0; i<xCoords.length; i++){ double xCoord = Double.parseDouble(xCoords[i]); } I receive the 08-04 11:40:30.435: ERROR/AndroidRuntime(1098): java.lang.NullPointerException. How can I extract the data? – Stefan Doychev Aug 4 '11 at 8:42
check value at xCoords[i].Print a log to see the value.Is there a problem with length or just it is because xCoords[i] is not double value? – Rasel Aug 4 '11 at 8:45
The problem is with the length - if I change the parameters of the for {} to for (int i=0; i<10; i++) the error moves to the next line - double xCoord = Double.parseDouble(xCoords[i]); – Stefan Doychev Aug 4 '11 at 8:47
then you have problem in length and also in xCooords[i],it is not always double – Rasel Aug 4 '11 at 8:53

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