Convert null object to String

Question

I have written an android program to load values to table-row from web service. But value comes null so I need to convert it into a string. Can someone tell me the method to do it?

try{                    

    SoapObject request = service.getRequest();
    SoapSerializationEnvelope envelope = service.getEnvelope(request);
    SoapObject response = service.getResponse(envelope);
    Log.i("Service Master", response.toString());
    int count = response.getPropertyCount();
    for (int i = 0; i < count; i++) {
        SoapObject result = (SoapObject) response.getProperty(i);
        DeleteuserDetails deleteuserDetails=new DeleteuserDetails();
        deleteuserDetails.setUserId(result.getPropertyAsString(4));
        deleteuserDetails.setUserName(result.getPropertyAsString(2));
        deleteuserDetails.setUserRole(result.getPropertyAsString(3));
        deleteuserDetails.setCreatedDate(result.getPropertyAsString(1));
        deleteuserDetails.setCreatedBy(result.getPropertyAsString(0));
        userdetail.add(deleteuserDetails);
    }

Now deleteuserDetails.setCreatedBy(result.getPropertyAsString(0)); gets null value from webservice, so I need to convert it into string "null".

LogCat:

12-20 18:48:52.608: W/System.err(2174): java.lang.NullPointerException
12-20 18:48:52.608: W/System.err(2174):     at org.ksoap2.serialization.SoapObject.getPropertyAsString(SoapObject.java:165)
12-20 18:48:52.608: W/System.err(2174):     at com.mvss.admin.Deleteuser$deteUserIdLoad.doInBackground(Deleteuser.java:81)
12-20 18:48:52.608: W/System.err(2174):     at com.mvss.admin.Deleteuser$deteUserIdLoad.doInBackground(Deleteuser.java:1)
12-20 18:48:52.608: W/System.err(2174):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
12-20 18:48:52.608: W/System.err(2174):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
12-20 18:48:52.608: W/System.err(2174):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
12-20 18:48:52.608: W/System.err(2174):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
12-20 18:48:52.608: W/System.err(2174):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
12-20 18:48:52.608: W/System.err(2174):     at java.lang.Thread.run(Thread.java:1096)

Solution 1

Use this,

try {
    deleteuserDetails.setCreatedBy(result.getPropertyAsString(0).toString());
}
catch(Exception e) {
    deleteuserDetails.setCreatedBy("null");
}

Solution 2

Instead of catching the exception or putting conditions, use String.valueOf(result.getPropertyAsString(0));

It will call toString() method of the argument and will convert it to String and if result.getPropertyAsString(0) is null, then it will change it to "null".

Solution 3

Although it's not a good practice, you can concatenate the null value with "" to make it a String.

For example:

String str=null;
System.out.println((str+"").length()); /// prints 4

Solution 4

result.getPropertyAsString(0) alone will result in a NPE already when the property is internally null. Your stacktrace points to SoapObject.getPropertyAsString(SoapObject.java:165) which should be

public String getPropertyAsString(int index) {
    PropertyInfo propertyInfo = (PropertyInfo) properties.elementAt(index);
    return propertyInfo.getValue().toString();
}

source - it will crash when propertyInfo or propertyInfo.getValue() is null.

To prevent that from happening you need to get the property not via getPropertyAsString but via getProperty and convert it manually to a String.

You can encapsulate that into some utility method

public static String getPropertyAsString(SoapObject object, int index) {
    Object prop = object.getProperty(index);
    if(prop instanceof PropertyInfo) {
        prop = ((PropertyInfo)prop).getValue();
    }
    return String.valueOf(prop); // will make it "null" if it is null
}

and then do

deleteuserDetails.setUserId(getPropertyAsString(result, getPropertyAsString(4)));
deleteuserDetails.setUserName(getPropertyAsString(result, getPropertyAsString(2)));
deleteuserDetails.setUserRole(getPropertyAsString(result, getPropertyAsString(3)));

Solution 5

Try this:

deleteuserDetails.setCreatedBy(result.getPropertyAsString(0) == null ? "null": result.getPropertyAsString(0));

View more solutions

Comments

[NickL]

Then you are still calling .toString() on getPropertyAsString. Which you can't do, because if getPropertyAsString returns null, it is like calling null.toString().

[Vivek Shankar]

could u please tell me elabrately

[Avadhani Y]

Place the condition as: if(result.getPropertyAsString(0).toString()!=null){deleteuse‌​rDetails.setCreatedB‌​y(result.getProperty‌​AsString(0).toString‌​());}

[NickL]

His problem is, that getPropertyAsString == null, so calling .toString() on that will cause a NPE.

[Avadhani Y]

ok @NickL then change the code as: if(result.getPropertyAsString(0)!=null){deleteuserDetails.se‌​tCreatedB‌​y(result.‌​getPropertyAsString(‌​0).toString());}

[NickL]

@Avadhani then the NULL value still isn't converted to a "null" String. See other answers.

[Avadhani Y]

@NickL What i am trying to tell is check whether the value result.getPropertyAsString(0) is null or not... thats it... if null return; else convert it to string... is it not the correct way to do....?

[NickL]

I know, but he wants to 'convert' the NULL value to a "NULL" String, a String which contains the text "NULL". In his current code he is trying to do this with .toString(), which ofcourse will throw a NPE when called on a NULL value.

[Vivek Shankar]

what can i do NickL and Avadhani

[Avadhani Y]

@user1858826 Please try to use the condition which i placed above and let me know if there are any issues....

[NickL]

Could do what Zapl said, it is the only answer that is different then the other 8 answers.

[Vivek Shankar]

try { deleteuserDetails.setCreatedBy(result.getPropertyAsString(0)‌​.toString()); } catch(Exception e) { deleteuserDetails.setCreatedBy("null"); }

[Vivek Shankar]

ya tried the above one and if exception rises i stored it as null

[Vivek Shankar]

stackoverflow.com/questions/13987579/…

[Vivek Shankar]

stackoverflow.com/questions/13987579/…

[NickL]

No, he caught the exception and then inserted "null". Like Gamb suggested. But @user1858826 is a bad user and probably isn't going to accept an answer anyways.

[Vivek Shankar]

who said NickL nothing like that

[Keith Tyler]

It may not be good practice, and I don't know why it might not be, but it certainly is effective, simple, reliable, and doesn't seem to have any negative side effects. Although I might advocate that the string value of null ought to be "".