Comparing Strings when one could be null

Question

am presently trying to get a response from a server which contains a response code of "00,02" i used an if and else if statement to perform an action for each of this response but am getting null pointer for the first if statement

if (str.equalsIgnoreCase("02")){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
}else if(str.equalsIgnoreCase("00")){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
}else{
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
}

It means, `str` is null. How are you assigning value to `str`? — Rohit5k2, Jun 05 '16 at 17:42
am getting the values directly from a json response, if the response does not have a responseCode then am to toast the response message out to the user, that is what the last else is meant to be for — henry, Jun 05 '16 at 19:52
In that case your first check should be for null. Check my answer. — Rohit5k2, Jun 05 '16 at 19:58
You might want a unique message for each case, if the code is to do anything useful... — Chris Stratton, Jun 05 '16 at 20:19
I'd recommend you change the title, it's quite misleading and very vague. — Vucko, Jun 05 '16 at 20:20
@njzk2 - don't close a question with answers which usefully address its **specific issue** as a duplicate of a generic one which only provides broad advice, **especially when the poster had already done what was advised there** by specifying the exact location of the NPE even from the original posted form of their question. — Chris Stratton, Jun 05 '16 at 21:30

score 6 · Accepted Answer · answered Jun 05 '16 at 20:13

6

A null-safe way of comparing strings would be:

if ("02".equalsIgnoreCase(str)) {
    ...
}

So just flip the strings in each of your conditions and you should be good to go!

answered Jun 05 '16 at 20:13

Marcin Koziński

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score 0 · Answer 2 · answered Jun 05 '16 at 19:57

Update your condition like this

if(str == null || str.length() == 0){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
}
else if (str.equalsIgnoreCase("02")){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
}else if(str.equalsIgnoreCase("00")){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
}
else{
    // Unknown code from server
}

score 0 · Answer 3 · answered Jun 05 '16 at 20:19

You can use the TextUtils.isEmpty(str) function like so:

if (!TextUtils.isEmpty(str)){

    if (str.equalsIgnoreCase("02")){
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
    }else if(str.equalsIgnoreCase("00")){
        Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
    }else{
    Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
    }
}

This function basically does this for you:

public static boolean isEmpty(@Nullable CharSequence str) {
    if (str == null || str.length() == 0)
        return true;
    else
        return false;
}

Which you could've done yourself, but it might be clearer this way.

also tried this and it worked, lol seems i have a lot of options — henry, Jun 06 '16 at 09:47
@henry enjoy coding, this was quite an easy question , that's why you ended up with multiple good answers. — Vucko, Jun 06 '16 at 10:21

Comparing Strings when one could be null

3 Answers3