Helpful NullPointerException messages

Definition

Since Java 14 (on by default from Java 15) a NullPointerException tells you exactly which part was null, for example "because the return value of Demo.findCity() is null". You no longer have to guess in a long chain of calls.

Example code

The exception now names the null part

class Demo {
    static String findCity() { return null; }

    public static void main(String[] args) {
        try {
            System.out.println(findCity().length());
        } catch (NullPointerException e) {
            System.out.println(e.getMessage());
        }
    }
}

// Output:
// Cannot invoke "String.length()" because the return value of "Demo.findCity()" is null