What is a Java Interface
interface specifies what a class must do, but not how it does it.
To implement an interface, a class must create the complete set of methods defined by the interface.
Defining an Interface
An interface is defined much like a class. This is the general form of an interface:
access interface name {
return-type method-name1(parameter-list);
return-type method-name2(parameter-list);
type final-varname1 = value;
type final-varname2 = value;
// ...
return-type method-nameN(parameter-list);
type final-varnameN = value;
}
Variables can be declared inside of interface declarations.
They are implicitly final and static.
They must also be initialized with a constant value.
All methods and variables are implicitly public if the interface, itself, is declared as public.
Here is an example of an interface definition.
interface MyInterface{
void callback(int param);
}