Finding Null or Empty String Checks in Java

I have a lot of code like this:

if( null == myString || "".equals(myString))
    doAThing();

Enter fullscreen mode Exit fullscreen mode

The codes fine, really. Very idiomatic, gets the job done.

Lately, I’ve been on a predicate kick. I like replacing my conditionals with predicates that describe the intent of the conditional statement. I can also replace a lot of my boilerplate code with a couple common predicates. This is one I use a lot:

 public static final Predicate<String> NULL_OR_EMPTY = (in) -> null==in || "".equals(in);

Enter fullscreen mode Exit fullscreen mode

It’s true; if the code base had been crafted with Optionals or other null-avoidance techniques, that I could mostly ignore this check. My code base has history and weight and external interfaces, so there are plenty of this check and others like it.

I have been using this regex to find likely places that I can apply my predicate:

  /\(\s*null\s*==\s*(\S*)\s*\|\|\s*""\.equals\(\s*\1\s*\)\s*\)|\(\s*(\S*)\s*==\s*null\s*\|\|\s*""\.equals\(\s*\2\s*\)\s*\)|\(\s*null\s*==\s*(\S*)\s*\|\|\s*\3\.equals\(\s*""\s*\)\s*\)|\(\s*(\S*)\s*==\s*null\s*\|\|\s*\4\.equals\(\s*""\s*\)\s*\)|\(\s*""\.equals\(\s*(\S*)\s*\)\s*\|\|\s*null\s*==\s*\5\s*\)|\(\s*(\S*)\.equals\(\s*""\s*\)\s*\|\|\s*null\s*==\s*\6\s*\)|\(\s*""\.equals\(\s*(\S*)\s*\)\s*\|\|\s\7\s*==\s*null\s*\)|\(\s*(\S*).equals\(\s*""\s*\)\s*\|\|\s*\8\s*==\s*null\s*\)|\(\s*null\s*==\s*(\S*)\s*\|\|\s*""\s*==\s*\9\s*\)|\(\s*(\S*)\s*==\s*null\s*\|\|\s*""\s*==\s*\10\s*\)|\(\s*null\s*==\s*(\S*)\s*\|\|\s*\11\s*==\s*""\s*\)|\(\s*(\S*)\s*==\s*null\s*\|\|\s*\12\s*==\s*""\s*\)|\(\s*""\s*==\s*(\S*)\s*\|\|\s*null\s*==\s*\13\s*\)|\(\s*(\S*)\s*==\s*""\s*\|\|\s*null\s*==\s*\14\s*\)|\(\s*""\s*==\s*(\S*)\s*\|\|\s*\15\s*==\s*null\s*\)|\(\s*(\S*)\s*==\s*""\s*\|\|\s*\16\s*==\s*null\s*\)/g

Enter fullscreen mode Exit fullscreen mode

It’s an ugly one, but it matches a lot of common patterns for checking if a string is null or empty. I’m hopeful that folks will suggest either a better way of finding null or empty checks or help me add to my hideous regex!

Get a monthly email with great tech and tech leadership articles from around the web

Thanks to Jan Tik for the header image

Follow me at my blog!

原文链接：Finding Null or Empty String Checks in Java