why interface methods cannot be declared as native or synchronized?

[michael wang]

i know that interface method cannot be declared as abstract,but i don'e know why interface methods cannot be declared as native or synchronized?

[Macon Pegram]

Interface methods merely describe a contract that an implementing class must fufill. They do not describe in any way the implementation details.
native and synchronized refer to implementation details that are not only not known, but also not relevant when specifying an interface.

[Valentin Crettaz]

You can also refer the following yesterday's discussion about the topic:
http://www.javaranch.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic&f=24&t=015080

[Macon Pegram]

You beat me to it Vallentin! I was just getting ready to post that exact same comment!
Macon