Can't i initialized empty String array and pass in the value afterwards in Java?

I can't seems to find out what what is wrong with my codes? i can't开发者_开发百科 pass in non-empty String value into an empty String array?

String[] profiles = wifiPositioningServices.GetAllProfileData();

ArrayList<String[]> macAddresses = new ArrayList<String[]>();
String[] macAddressTemp=null;

    //store all profile data into a ArrayList of Profile objects
    for(int i=0; i<profiles.length; i++){
        String[] result = profiles[i].split(",");
        Profile profile = new Profile();
        profile.setProfileName(result[0]);
        profile.setOwner(result[1]);
        profile.setMap(result[2]);
        profile.setVisible(result[3]);
        boolean visible = Boolean.valueOf(result[3]);
        if(visible){
            //if visible is true, then add profile name and mac filters into arraylist 
            profileNames.add(result[0]);
            int cnt=0;
            for(int j=4; j<result.length; j++){
                profile.setMacFiltersList(result[j]);
                Log.e("Text:", result[j]);
                macAddressTemp[cnt] = result[j];
                ++cnt;
            }
            macAddresses.add(macAddressTemp);
        }
        profileList.add(profile);
    }

Java show a nullpointer exception at the line "macAddressTemp[cnt] = result[j];". I am sure that result[j] is not empty cause i was able to print it out via the log msg.

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Use an ArrayList instead.

ArrayList<String> macAddressTemp = new ArrayList<String>(100); //check capacity
macAddressTemp.add(result[j]);

EDIT:

You changed your code wrong. This ArrayList<String[]> macAddresses = new ArrayList<String[]>(); is creating a List that contains arrays. You have to create a List that contains String. Check the code above.

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The array macAddressTemp is null.

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The NPE is thrown because macAddressTemp is null. You probably want to declare and initialize macAddressTemp inside of the outer loop.

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You explicitly set it to null:

String[] macAddressTemp=null;

You need to allocate some space for the array, or use a collection.