Difference between string.equalsIgnoreCase(object.string) vs object.string.equalsIgnoreCase(string)

Question

Let's say I have a class:

public class MyClass {
    String locale;

    public String getLocale(){
        return this.locale;
    }

    public setLocale(String locale){
        this.locale = locale;
    }
}

Now I have been told that there is a difference in following statements

1. myClass.getLocale().equalsIgnoreCase("en")

2. ("en").equalsIgnoreCase(myClass.getLocale())

I have been trying to find the search for it but unable to do so. Can anyone help me with an explanation of what is the difference?

Is there a particular difference in execution time? And also which of these two is the best practice

Answer 1

myClass.getLocale().equalsIgnoreCase("en") throws NullPointerException when myClass.locale is null.

("en").equalsIgnoreCase(myClass.getLocale()) does not compile.

If you are talking about "en".equalsIgnoreCase(myClass.getLocale()), it works fine when myClass.locale is null. false will be returned.

Answer 2

The only difference I spot is that in the first example the statement myClass.getLocale() is not null-safe, thus somehow might return null and it would lead to the NullPointerException.

The second one is safe since you call a method on "en", which is never null and will not fail even if you pass a null to the method with myClass.getLocale().

---

Edit: Both of the explanations assume that the myClass is not null itself, thus only getLocale() would fail. Noone of the solutions is null-safe in case the myClass is null - then the NPE will be thrown anyway. (@davidxxx)