Java Interface Overview
Interface: Interfaces can be used to implement the Inheritance relationship between the non-related classes that do not belongs to the same hierarchy, i.e. any Class and any where in hierarchy. Using Interface, you can specify what a class must do but not how it does.
- A class can implement more than one Interface.
- An Interface can extend one or more interfaces, by using the keyword extends.
- All the data members in the interface are public, static and Final by default.
- An Interface method can have only Public, default and Abstract modifiers.
- An Interface is loaded in memory only when it is needed for the first time.
- A Class, which implements an Interface, needs to provide the implementation of all the methods in that Interface.
- If the Implementation for all the methods declared in the Interface are not provided , the class itself has to declare abstract, other wise the Class will not compile.
- If a class Implements two interface and both the Intfs have identical method declaration, it is totally valid.
- If a class implements tow interfaces both have identical method name and argument list, but different return types, the code will not compile.
- An Interface can't be instantiated. Intf Are designed to support dynamic method resolution at run time.
- An interface can not be native, static, synchronize, final, protected or private.
- The Interface fields can't be Private or Protected.
- A Transient variables and Volatile variables can not be members ofInterface.
- The extends keyword should not used after the Implements keyword, the Extends must always come before the Implements keyword.
- A top level Interface can not be declared as static or final.
- If an Interface species an exception list for a method, then theclass implementing the interface need not declare the method withthe exception list.
- If an Interface can't specify an exception list for a method, the class can't throw an exception.
- If an Interface does not specify the exception list for a method, he class can not throw any exception list.
- Further information can be found at:
http://www.abapprogramming.net
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