Uninitialized variables and members in Java

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The language defines it this way.

Instance variables of object type default to being initialized to null.
Local variables of object type are not initialized by default and it’s a compile time error to access an undefined variable.

See section 4.12.5 for SE7 (same section still as of SE14)
http://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.12.5

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