INTERVIEW QUESTIONS J2EE JAVA DETAILS

Question: If interface has got four methods,and I like to implement only two methods, how this could be achieved?

Answer: I have an idea. But I am not sure if it is the right answer. Can I divide these 4 methods into 2 interface? Then I can only implement the wanted 2 methods.

I have an idea. But I am not sure if it is the right answer. Can I divide these 4 methods into 2 interface? Then I can only implement the wanted 2 methods. Source: CoolInterview.com

Directly implement those two methods and leave the remaining two in a new class which can implements the given interface. Source: CoolInterview.com

It is not possible.The rule of the interface is that we have to overide all the methods present in it.If we fail, the complier will show the error. We have the concept of adapter classes in java. In this adapter classes, if an listener interface has many methods in that case we can use the corresponding adapter class to implement only the requried methods. But for user defined interfaces there is no such option.So it is not possible. Source: CoolInterview.com

Hi...
We can achieve this scenario by marking the class as a "Abstract", Abstract class is eligible for having the both "concrete" methods(A method with body) as well as "Abstract" methods.So u can implement the two methods whatever u want and other methods should be abstract. So the class should be abstract .Observe the following program.

public interface Sample
{
public void display();
public void getData();
public void putData();
public void devarathnam();
}
public abstract class Example implements Sample{
abstract public void display();
abstract public void getData();

public void devarathnam()
{
System.out.println(" Hi Devarathnam");
}
public void putData()
{
System.out.println(" Some data");
}
}
Source: CoolInterview.com

yes, we can implement this concept as interface implement in class by giving body of require methods and leave blank to other two method as:
interface i1{
void d1();
void d2();
void d3();
void d4();
}
class useinterface implements i1
{
void d1()
{ System.out.println("d1");
}
void d2()
{ System.out.println("d2");
}

void d3()
{ }
void d4()
{ }

pulic static void main(String args[])
{
}
}
Source: CoolInterview.com

when a class implements one interface it must implement(define) all the methods which have declared in the interface.
you can't implement two methods if the interface contain four methods.
for example take a Servlet interface,when we implement the Servlet interface in our class we must implement all the methods of Servlet interface(the methods init(),service(),destroy(),getServletInfo(),getServletContext()),but when we extend a GenericServlet class into our class we can use some methods of the GenericServlet class like service(). Source: CoolInterview.com

a class must implement all the methods in an interface or be an abstract class. Source: CoolInterview.com

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