java / android NullPointerException thrown on a String

Question

I have what seems like a very simple method, written in java for an android application:

EDIT 1: private String newResponse;

public SOME METHOD CALLED FIRST
{
    newResponse = "";
}

END OF EDIT 1

public synchronized void reportMessage(String message)
{
    try
    {
        newResponse = newResponse + message;

        confirmQE(); //Look for qe in the message
    }
    catch (Exception e)
    {
        response = e.getCause().toString();
    }
}

When I run the application in debugger mode, it 'suspends' on the line:

newResponse = newResponse + message;

It says in the debug window:

Thread[<9> Thread-10] (Suspended (exception NullPointerException))

This occurs only some of the time. Sometimes it runs the line fine.

It never goes into the catch clause and when you click continue, the app crashes. There isn't a break point on the line so I don't even know why it is suspending there.

newResponse is of type String, defined as a global variable.

Can anyone help?

what is the value of newResponse and message when the application crashes? — Tomer
– Tomer, Commented Jul 23, 2012 at 13:04
are you creating string as "String newResponse" if yes, than you have to initialized to "String newResponse=''" . I hope it will work — Roll no1
– Roll no1, Commented Jul 23, 2012 at 13:06
Sorry @AndroidCoader, I forgot to add code that occurs earlier. I think what I have is sufficient to initialise it correctly. — Pippa Rose Smith
– Pippa Rose Smith, Commented Jul 23, 2012 at 13:21
@ftom2 The value of newResponse is "" and the value of message is ÌÌÌÎfffffs3333ÌÌÌÍÌÌÌÌæffs3333Æs33ÌÌÍ³33æfs333Ì³33æ..... (1024 characters long) which looks weird but is what it is supposed to be. — Pippa Rose Smith
– Pippa Rose Smith, Commented Jul 23, 2012 at 13:23

Chintan Raghwani · Accepted Answer · 2012-07-23 13:46:13Z

5

try
    {
        // NOW add following condition and initialize newResponce only when it is null
        if(null == newResponse)
        {
            newResponse = new String();
        }
        System.out.println("newResponse"+newResponse);  //<--Add this two lines
        System.out.println("message"+message); // and check which line gives you NullPointerException

        newResponse = newResponse + message;

        confirmQE(); //Look for qe in the message
    }

edited Jul 23, 2012 at 13:46

answered Jul 23, 2012 at 13:04

Chintan Raghwani

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7 Comments

Pippa Rose Smith Over a year ago

Sorry, but that doesn't seem to help. I have added what you suggested but I think my initialisation that I have already was sufficient, see edit 1 in code.

Chintan Raghwani Over a year ago

See your question. I HAVE EDITED IT and try that then say.

Pippa Rose Smith Over a year ago

I can't have newResponse initialised in that method as sometimes newResponse = "actual text" before the method is run. WHen I add System.out.println(newResponse); and System.out.println(message) in before newResponse = newResponse + message;, it is suspended on System.out.println(newResponse);

Chintan Raghwani Over a year ago

and some time you don't initialize newResponse with any text ?? Am I right? So that time you are getting NullPointerException.

Pippa Rose Smith Over a year ago

yes, sometimes newResponse = "". But I want it just just = blank not equal null

|

Mitul Nakum · Accepted Answer · 2012-07-23 13:04:36Z

2

public synchronized void reportMessage(String message)
{
    try
    {
        if(newResponse == null){
            newResponse = message;
        }else{
            newResponse = newResponse + message;
        }

        confirmQE(); //Look for qe in the message
    }
    catch (Exception e)
    {
        response = e.getCause().toString();
    }
}

Try above code..

answered Jul 23, 2012 at 13:04

Mitul Nakum

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8 Comments

Pippa Rose Smith Over a year ago

Now it is doing the same thing on the line: if(newResponse == null){

Mitul Nakum Over a year ago

try if(newResponse.equals(null)){

cHao Over a year ago

if (newResponse == null) should not cause a NullPointerException. In fact, that is one of the very few legit ways to check whether a reference is null.

Mitul Nakum Over a year ago

yes, that's what I think. Still we can check other way by using if(newResponse.equals(null))

Pippa Rose Smith Over a year ago

Nope, still the same. And I tried putting "" instead of null in both cases as well.

|

wrschneider · Accepted Answer · 2012-07-23 13:04:18Z

0

Inspect the individual variables to see which one is null.

Also, e.getCause() may be returning null also, so you may have an exception inside your exception handler as well.

answered Jul 23, 2012 at 13:04

wrschneider

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1 Comment

Pippa Rose Smith Over a year ago

Neither appears to be null. newResponse = "" but that should be al-right shouldn't it?

Pippa Rose Smith · Accepted Answer · 2012-07-25 09:59:07Z

0

I have fixed the problem.

For anyone wondering, I added

if("".equals(newResponse))
{ 
    newResponse = new String();
}

before

newResponse = newResponse + message;

And that prevents the error.

Thanks for everyone's help.

answered Jul 25, 2012 at 9:59

Pippa Rose Smith

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