Collections.sort comparing 2 objects throws null pointer exception

Question

i am using collections.sort methods int compare to compare 2 objects distance parameter and sort them according to distance in ascending order. here is what i am doing to compare it

Collections.sort(venuesList, new Comparator<FoursquareVenue>() {

                @Override
                public int compare(FoursquareVenue lhs, FoursquareVenue rhs) {                  


                    return lhs.getDistance().compareTo(rhs.getDistance());  
                }
            });

I think there is just some small silly thing i am missing to do but i couldn't figure it out whats the problem error says something like this

07-12 14:52:51.018: E/AndroidRuntime(1377): FATAL EXCEPTION: main
07-12 14:52:51.018: E/AndroidRuntime(1377): java.lang.NullPointerException:println needs a message
07-12 14:52:51.018: E/AndroidRuntime(1377): at android.util.Log.println_native(Native Method)
07-12 14:52:51.018: E/AndroidRuntime(1377): atandroid.util.Log.v(Log.java:117)

I think i need to handle the null values of the object but i don't know how can i do that?

Titus · Accepted Answer · 2015-07-12 06:21:35Z

1

The second argument to Log.v(...) needs to be a String and the getDistance() method probably returns null

To prevent the exception you can do something like this:

if (lhs != null && rhs != null && lhs.getDistance() != null && rhs.getDistance() != null) {
    Log.v("lhs Distance", lhs.getDistance());
    Log.v("rhs Distance", rhs.getDistance());
    return lhs.getDistance().compareTo(rhs.getDistance());
} else {
    return -1;
}

edited Jul 12, 2015 at 6:21

answered Jul 12, 2015 at 5:40

Titus

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5 Comments

Christian Young Over a year ago

Actually it is what you said.. it still throws same exception and how should i handle that if getDistance is returning null value...

Titus Over a year ago

@ChristianYoung Yes, I've changed my answer, it may be returning null hence the NullPointerException

Christian Young Over a year ago

you are right i just saw in Logcat that when lhs.getDistance returns null it shows null pointer exception so what should i do to handle that?

Christian Young Over a year ago

Log.v is just to print the output on my console to figure out whats wrong changing those value didn't effect the error i need to solve the return statement... consider Log.v statement is not in code

Titus Over a year ago

@ChristianYoung I've edited my question again, the Log.v(...) method was the one causing the error but I guess by fixing it you got another NullPointerException because lhs.getDistance() returned null when you were trying to compare it lhs.getDistance().compareTo(...)

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