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which method to use?

Paul Villangca
Ranch Hand

Joined: Jun 04, 2002
Posts: 133
from sanjayahuja.tripod.com (with modifications)

I thought this would be a compile error, 'coz method(null) would be ambiguous (it wouldn't know which method() will be invoked.) But it compiles and prints out "Integer Version" when run! Also, when method(String) is uncommented out, then the compiler complains about ambiguous methods.
Tybon Wu
Ranch Hand

Joined: Jun 18, 2002
Posts: 84
Note the inheritance tree:
Object
|
+-Number
++|
+++-Integer
Since null is compatible to any object, the one furthest down the compatible path will be chosen, in this case, Integer.
If you also have the overloaded method with the String parameter, then that will create two compatible paths for null, which causes the ambiguous methods error.
[ June 19, 2002: Message edited by: Tybon Wu ]

SCJP2
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: which method to use?