A better way to compare Strings which could be null [duplicate]

Question

I was just wondering if there is a better way to do this. i feel it might be inefficient. Problem is for DB reasons i need to compare strings which can sometimes be null or not.

public static boolean compareStrings(String str1, String str2){

    if(str1 == null && str2 == null) return true;

    if(str1 != null && str2 != null){
        if(str1.equals(str2))
            return true;
    }

    return false;
}

Answer 1

The usual idiom is this:

return (str1 == null ? str2 == null : str1.equals(str2));

Answer 2

You say that these are potentially coming from a database. At that point, any inefficiencies around a few nullity tests are entirely insignificant compared with the cost of database queries, to be honest. I would focus on the readability.

To that end, I would start using Guava and its Objects class:

boolean equal = Objects.equal(a, b);

I would expect that to be implemented as per Taymon's code, basically - but it's nice to have it in one place.

EDIT: For Java 7+ you don't need Guava. You can just use java.util.Objects.equals(a, b).

Answer 3

If you are open to using apache Commons StringUtils then they have equals which compares two strings null-safe

Answer 4

This code would only be inefficient if it causes a bottleneck during a normal execution of your program. The only way to know if this is the case is to run your program through a profiler. Until you do that and see for a fact that this function causes performance problems, I wouldn't worry about it.