[java] Should I use string.isEmpty() or "".equals(string)?

I'm usually testing this alongside a string == null, so I'm not really concerned about a null-safe test. Which should I use?

String s = /* whatever */;
...
if (s == null || "".equals(s))
{
    // handle some edge case here
}

or

if (s == null || s.isEmpty())
{
    // handle some edge case here
}

On that note - does isEmpty() even do anything other than return this.equals(""); or return this.length() == 0;?

One thing you might want to consider besides the other issues mentioned is that isEmpty() was introduced in 1.6, so if you use it you won't be able to run the code on Java 1.5 or below.

You can use apache commons StringUtils isEmpty() or isNotEmpty().

It doesn't really matter. "".equals(str) is more clear in my opinion.

isEmpty() returns count == 0;

String.equals("") is actually a bit slower than just an isEmpty() call. Strings store a count variable initialized in the constructor, since Strings are immutable.

isEmpty() compares the count variable to 0, while equals will check the type, string length, and then iterate over the string for comparison if the sizes match.

So to answer your question, isEmpty() will actually do a lot less! and that's a good thing.

I wrote a Tester class which can test the performance:

public class Tester
{
    public static void main(String[] args)
    {
        String text = "";

        int loopCount = 10000000;
        long startTime, endTime, duration1, duration2;

        startTime = System.nanoTime();
        for (int i = 0; i < loopCount; i++) {
            text.equals("");
        }
        endTime = System.nanoTime();
        duration1 = endTime - startTime;
        System.out.println(".equals(\"\") duration " +": \t" + duration1);

        startTime = System.nanoTime();
        for (int i = 0; i < loopCount; i++) {
            text.isEmpty();
        }
        endTime = System.nanoTime();
        duration2 = endTime - startTime;
        System.out.println(".isEmpty() duration "+": \t\t" + duration2);

        System.out.println("isEmpty() to equals(\"\") ratio: " + ((float)duration2 / (float)duration1));
    }
}

I found that using .isEmpty() took around half the time of .equals("").