Interfaces in java

v                       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 of  Interface.
•   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 the  class implementing the interface need not declare the method with  the 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.

The general form of Interface is

Access interface name {

         return-type method-name1(parameter-list);

            type final-varname1=value;

          }

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Marker Interfaces :  Serializable, Clonable, Remote, EventListener,

Java.lang is the Package of all classes and is automatically imported into all Java Program

Interfaces:  Clonable , Comparable, Runnable