String comparison order in Java

Question

Are both the String comparison methods below considered to be equal

public class TestString {
    public static final String CONSTVAL="foo";

    public boolean testString1(String testVal) {
        return testVal.equalsIgnoreCase(CONSTVAL);
    }

    public boolean testString2(String testVal) {
        return CONSTVAL.equalsIgnoreCase(testVal);
    }
}

or should one type of comparison be favoured over another?

Answer 1

One advantage of the latter is that it won't throw an exception if testVal is null.

I would expect the results to be the same, other than that.

Answer 2

You should call equals on the constant since it avoids the risk of NullPointerException when testVal is null.

public boolean testString2(String testVal) {
    return CONSTVAL.equalsIgnoreCase(testVal);
}

Answer 3

When a constant value compare itself to another value you're almost sure to not have null value.

In your case,

new TestString().testString1(null);

will throw an exception, whereas,

new TestString().testString2(null);

wont.

But this kind of notation could be considered as a yoda condition.

Answer 4

At first glance I would agree with @Jon Skeet, but then I noticed that CONSTVAL isn't final.

If it was final then testString2() is the safest and best way to test for equality.