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?
>Solution :
EDIT – Adding John Bollinger’s excellent comment snipped –
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:
How to initialize an array in Java?
Boxing and unboxing:
https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html