I must admit this had never occurred to me before but after reading, the explanation seems so obvious!
You can get NullPointerException from lines in Java which appear to have no possibility of throwing them, such as;
this.setCount(num)
The null pointer exception can come about when num is of type Integer and setCount takes an int parameter. Java’s auto-boxing will automatically call num.intValue(), and if num is null you get an exception.
Of course, the fix is to check for null-ness and treat it however the semantics of your operation requires.
From the SDE Tip – Amazon
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