Java Interface

-

 INTERFACE: 

  • An Interface In java is a blueprint of a class.
  • Interface contain final and static variables by default (Static: the variable can be directly accessed with-out creating an object that is a common Variable for all the class and Final: that variable value is constant we cannot change “ We no need to specify static, final keywords by default the variable treated as static & final ”).
  • Interface contain Abstract Methods(Abstract Method: the method which contain only definition not the body ” We can’t implement the body ”).
  • Methods in Interface are Public(access specifier) by default.
  • Interface supports the functionality of Multiple Inheritance.
  • We can define Interface with Interface keyword.
  • A class extends another class(by using extend keyword), An Interface extends another Interface but A class Implements an Interface(only interface without implementation-class(A class implements the interface with Implements key word) there is no use).
  • We can create Object reference for Interface but We can not instantiate Interface.

Example:


  interface A 

{

int a=10; // by default variables in interface are static and final

void m1(); // abstract method, by default public

}


 public class Test implements A

{

public void m1()

{

System.out.println(a);

}


public static void main(String[ ] args) 

{

/* Test t=new Test() ; // this is one way of creating object through class ‘Test’ and                                             calling method “m1()” through that Object.

t.m1(); */


A a=new Test(); // through Interface we can create object reference but we can                                         not instantiate  so we use Test class here instead of interface.

a.m1() ;

}

}

Comments

Post a Comment

Popular posts from this blog

Data-sly-list & Data-sly-repeat

-
Image
  AEM Sightly : Data-sly-list : the most powerful block statement of sightly which iterate the collection return from the slingModel.  Data-sly-list can handle any kind of collection like: Example : <div  data-sly-use. variable_name =“com.aem.package_name.core.models.Interfaceclass_name”></div>// this is used to call the slingModel <div data-sly-list. item =“${ variable_name . InterfaceMethod_Name}”> // item is the default variable provided by Slightly & you can give any name ${ item } </div> *note: Map don’t give ordered list, It gives random list. —> We can control loop’s in slightly using begin, end. Example: <div data-sly-list. item =“${ variable_name .InterfaceMethod_Name @ begin =0, end =3}”>  // the loop gives 4 values ${ item } </div>  —> Slightly provide some methods like: count, even, odd, middle…etc. Example: <div data-sly-list. item =“${ variable_name .InterfaceMethod_Name}”> ${ ite...
Read more

Java HashMap

-
  HashMap: HashMap contain data in form of : Keys & Values = Pair(we call it as Pair) Key’s should be Unique and Values can be duplicate. The Keys and Values can be any DataType. To Store Pairs in a variable that should be a “ Map.Entry ” DataType like Object datatype in ArrayList. To read the values from the “ Map.Entry Variable ” we should use methods like: variable.getKey(); variable.getValue() ; * Note:   the name of the Object becomes the name of the HashMap.      ▪  HashMap Declaration : Two ways we can declare HashMap. To Store any DataType of pairs(key, value): HashMap objectName = new HashMap(); Example: HashMap obj = new HashMap();     2.  To Store Required DataType of pairs(key, value):             HashMap <key _DataType, value_DataType>   objectName = new HashMap                <key _DataType, value_DataType> ();  ...
Read more

Java Packages

-
Java Packages: A Java Package is a simple kind of a folder which contain a similar   kind of classes, Suppose a classes which are belongs to some functionality will be there in one package the other classes which are belongs to other functionality belongs to other packages. And later if you want to get that class in some other class we will refer that class by using Package Name, So a Java Package is a collection of classes,Interfaces or some files. In realTime the PackageName are like com.ProjectName.CompanyName like this . So If there are two packages with classes:  Package1 {classA, classB,….} & Package2{classX, classY,….}: To access classA from Package2 we need Import & extend keywords Syntax: Import PackageName.className; classX extend classA { // here we can use classA } How to create Sub-Package: Right click on parent package and click on   New—>Package: give name as  “Parent-PackageName.Sub-PackageName” and Finish. These ...
Read more