Check two arguments in Java, either both not null or both null elegantly

Question

I used spring boot to develop a shell project used to send email, e.g.

sendmail -from [email protected] -password  foobar -subject "hello world"  -to [email protected] 

If the from and password arguments are missing, I use a default sender and password, e.g. [email protected] and 123456.

So if the user passes the from argument they must also pass the password argument and vice versa. That is to say, either both are non-null, or both are null.

How do I check this elegantly?

Now my way is

if ((from != null && password == null) || (from == null && password != null)) {     throw new RuntimeException("from and password either both exist or both not exist"); } 

Answer 1

There is a way using the ^ (XOR) operator:

if (from == null ^ password == null) {     // Use RuntimeException if you need to     throw new IllegalArgumentException("message"); } 

The if condition will be true if only one variable is null.

But I think usually it's better to use two if conditions with different exception messages. You can't define what went wrong using a single condition.

if ((from == null) && (password != null)) {     throw new IllegalArgumentException("If from is null, password must be null"); } if ((from != null) && (password == null)) {     throw new IllegalArgumentException("If from is not null, password must not be null"); } 

It is more readable and is much easier to understand, and it only takes a little extra typing.