Weird behaviour when using Java ternary operator

Question

When I write my java code like this:

Map map = new HashMap<>()
Long number =null;
if(map == null)
    number = (long) 0;
else
    numbe         


        

Answer 1

What is happening here? Both these code paths are exactly equivalent isn't it?

They are not equivalent; the ternary operator has a few caveats.

The if-true argument of the ternary operator, (long) 0, is of the primitive type long. Consequently, the if-false argument will be automatically unboxed from Long to long (as per JLS §15.25):

If one of the second and third operands is of primitive type T, and the type of the other is the result of applying boxing conversion (§5.1.7) to T, then the type of the conditional expression is T.

However, this argument is null (since your map does not contain the string "non-existent key", meaning get() returns null), so a NullPointerException occurs during the unboxing process.