Why does this code give a null pointer Exception? I thought Character class could handle null being assigned?

Question

public class Playground {
  public static void main(String[] args) {
    String s = "blah";
    Character lclfs = s.contains("/") ? '/' : s.contains("\\") ? '\\' : null;
  }
}

What am I missing (using Java 1.8)?

Answer 1

That is because your code will try to unbox null. Using IntelliJ this will be shown directly as warning: "Unboxing of null may produce NullPointerException".

An alternative would be to do it like this:

String s = "blah";
Character lclfs = s.contains("/") ? Character.valueOf('/') : 
    s.contains("\\") ? Character.valueOf('\\') : null;

As @Antoniossss pointed out, this would also help:

String s = "blah";
Character lclfs = s.contains("/") ? Character.valueOf('/') : 
    s.contains("\\") ? (Character)'\\' : null;

Talking about warnings in IntelliJ, my above code is now saying: ”Unnecessary boxing 'Character.valueOf('\')'”. So probably you should try to refactor your code. Instead of using explicit null, you could introduce java.util.Optional:

Optional<Character> lclfs = s.contains("/") ? Optional.of('/') :
        s.contains("\\") ? Optional.of('\\') : Optional.empty();