CODEWITHSUNDEEP
androidlogging
choman
choman

Reputation: 787

Log.d doesn't print out message

I get an error java.lang.NullPointerException: println needs a message when using Log statement with the following code 

 for (Application app : mApplications) {
            Log.d("LOG", "********");
            Log.d("LOG", app.getName());
            Log.d("LOG", app.getArtist());
            Log.d("LOG", app.getReleaseDate());

        }

but in second parameter, If I add another string between quotes the error is gone

for(Application app: mApplications){
            Log.d("LOG", "******************");
            Log.d("LOG","Name: " +app.getName());
            Log.d("LOG","Artist: " +app.getArtist());
            Log.d("LOG","ReleaseDate: " +app.getReleaseDate());

        }

what is the difference between the two ?

Upvotes: 0

Views: 606

Answers (2)

Vishal Senjaliya
Vishal Senjaliya

Reputation: 456

First of all if you are using Log.d it is generally use for debugging and this is the correct syntax for Log.d d(String tag, String msg, Throwable tr) For better understanding See this

In your case First you are using this 

for (Application app : mApplications) {
        Log.d("LOG", "********");
        Log.d("LOG", app.getName());
        Log.d("LOG", app.getArtist());
        Log.d("LOG", app.getReleaseDate());

    }

And generate this error java.lang.NullPointerException: println needs a message because you can't put message as per Log.d syntax rule.

I hope you understand...

Upvotes: 0

OneCricketeer
OneCricketeer

Reputation: 191681

The difference is that you've concatenated a string with the a null variable.

Log needs a non-null message string.

Alternatively, this also works because it will print "null" but it doesn't look clean 

Log.d("LOG", String.valueOf(app.getName()));
Log.d("LOG", String.valueOf(app.getArtist()));
Log.d("LOG", String.valueOf(app.getReleaseDate()));

Upvotes: 1

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