Why does this line produce a nullpointer? Java 15

Question

The following two lines:

   Boolean visitedAlphabet[] = new Boolean[26];
   Arrays.stream(visitedAlphabet).anyMatch(e -> e != true);

Produce a nullpointer, the second line to be specific:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because "<parameter1>" is null

Could you please tell me why this happens?

The Boolean objects in the array have not been initialized? Try logging the value of `visitedAlphabet[0]` after creation — blurfus, Oct 13 '22 at 23:39

mikeb · Accepted Answer · 2022-10-14T01:04:37.717

5

EDIT - Adding John Bollinger's excellent comment snippet -

Because e is null and the runtime is trying to "unbox" it to a primitive boolean.

You can either do (e != null && e != true) or !Boolean.TRUE.equals(e) or initialize your array:

Initialize an array stuff:

Boxing and unboxing:

edited Oct 14 '22 at 01:04

answered Oct 13 '22 at 23:41

mikeb

5

Or `!Boolean.TRUE.equals(e)`. That handles nulls naturally. – John Bollinger Oct 13 '22 at 23:46

1 Answers1