Some Useful Rules For Interface

As I found some Rules for Java Interfaces, which is very useful for any java programmer, I am publishing it here. If you have some more idea please do send me.

The rules go like this:

• The entire interface is implicitly public and abstract. That means, we do not need to type public or abstract modifier in the member methods.
• All variable defined in a interface must be public, static, and final. That means, interface can define only constant not instance variable.
• Interface method must not be static.
• As interface methods are abstract, they cannot be marked final, strictfp, or native.
• An interface can extend one or more other interfaces.
• An interface cannot extend anything but another interface.
• An interface cannot implement another interface or class.
• An interface must be declared with the keyword interface.
• Interface types can be used polymorphically