Why I whine about return null

You may hear me go crazy when I see a return null; statement in the code. Unfortunately I've learned it the hard way. Whenever you have a possible null pointer, you need to check for it and add another path of execution to handle it.

Look at this code:

	public class Greeter {
	public String greetMessage(User user) {
	if(StringUtils.isEmpty(user.email())) {
	return null;
	}
	return "Hi, "+user.email();
	}
	}

view raw Greeter.java hosted with ❤ by GitHub

	public class GreetPrinter {
	public void static main(String[] args) {
	User user = new User();
	if (args.length > 1) {
	user.setEmail(args[0]);
	}
	Greeter greeter = new Greeter();
	String msg = greeter.greetMessage(user);
	if (msg != null) {
	System.out.println(msg);
	}
	}
	}

view raw GreetPrinter.java hosted with ❤ by GitHub

	public class User {
	private String email;
	public void setEmail(String email) {
	this.email = email;
	}
	public String email() {
	return email;
	}
	}

view raw User.java hosted with ❤ by GitHub

Can you count how many extra paths are there because of the null check? 2 extra conditions, and 1 extra collaborator (The StringUtils) to check for a null string.

Now look at the next code.

	public class Greeter {
	public String greetMessage(User user) {
	return "Hi, "+user.email();
	}
	}

view raw Greeter.java hosted with ❤ by GitHub

	public class GreetPrinter {
	public void static main(String[] args) {
	if (args.length < 1) {
	throw new RuntimeException("No email");
	}
	User user = new User(args[0]);
	Greeter greeter = new Greeter();
	System.out.println(greeter.greetMessage(user));
	}
	}

view raw GreetPrinter.java hosted with ❤ by GitHub

	public class User {
	private String email = "";
	public User(String email) {
	this.email = email;
	}
	public String email() {
	return email;
	}
	}

view raw User.java hosted with ❤ by GitHub

Doesn't that seem more stable? It's not hard to avoid return nulls, but it takes some discipline.
If you're still not convinced, listen to the guy who invented the null pointers:
http://www.infoq.com/presentations/Null-References-The-Billion-Dollar-Mistake-Tony-Hoare