Program to create a interface 'printable' and implement it in 'InterfaceDemo' class

Interface looks like class but it is not a class. An interface can have methods and variables just like the class but the methods declared in interface are by default abstract (only method signature, no body). Also, the variables declared in an interface are public, static & final by default. The interface in java is a mechanism to achieve fully abstraction.

 The class that implements interface must implement all the methods of that interface. Also, java programming language does not support multiple inheritance, using interfaces we can achieve this as a class can implement more than one interfaces. It cannot be instantiated just like abstract class. To achieve multiple inheritance in Java you have to use interface. The syntax for declaring interface is given below:
interface <interface-name> {
    // variable declarations
 // Method declarations (no implementation)
}

The implements keyword is used to for implementing interface and extends keyword is used to extend the class. The syntax for extending class and implementing interface is:
class <subclass-name> extends <superclass-name> implements <interface-name> {

 // Body of subclass
}

In this program, we have created an interface printable which has one method print( ) without implementation (body). Then we declare the class InterfaceDemo which implements printable interface and override (implement) the print( ) method in it. You must override all the methods which a interface contains. In main( ) method we have created an object of InterfaceDemo class and call the print( ) method.
PROGRAM
interface printable {
 
 void print();
}

public class InterfaceDemo implements printable {

 @Override
 public void print() {
  
  System.out.println("Hello");
 }
 
 public static void main(String[] args) {
  
  InterfaceDemo i = new InterfaceDemo();
  i.print();
 }
}
OUTPUT 
C:\>javac InterfaceDemo.java
C:\>java InterfaceDemo
Hello

Comments

Post a Comment

Popular posts from this blog

Program to define a class 'employee' with data members as empid, name and salary. Accept data for 5 objects using Array of objects and print it.

This program demonstrates you the array of objects.  Array of object  is the collection of objects of the same class. The given syntax will define an array of reference therefore assign object to individual reference in the array to declare the array of object. The syntax to define array of object is: <class-name> <array-name> [size]; For example, the following statement will define an array of object having size 6 references to the class  Box . Box b[6]; For creating an array of objects (allocating memory) you have to write down the following statements for (int i=0; i<6; i++) { b[i] = new Box(); // Assigning object to individual reference in the array. } PROGRAM import java.util.Scanner; public class Employee { int empid; String name; float salary; public void getInput() { Scanner in = new Scanner(System.in); System.out.print("Enter the empid :: "); empid = in.nextInt(); System.out.print("Enter the name :: ");
Read more

Program to input age from user and throw user-defined exception if entered age is negative

An  Exception  is an abnormal condition that arises in a code sequence at run time. Exceptions are run time errors. Exceptions generated by the Java are related to the fundamental errors that violate the Java language constraints. All exception classes are subtypes of the  java.lang.Exception  class. The exception class is a subclass of the  Throwable  class. Java defines several exception classes inside the standard package  java.lang . Some examples of exceptions are  ArithmeticException, ArrayIndexOutOfBoundsException, IndexOutOfBoundsException, NullPointerException, NumberFormatException, ClassNotFoundException,etc. When Java Interpreter caught an error such as divide by zero, the interpreter creates an exception object and throws it to inform that an error has occurred. Java has its own exception handling mechanism. It performs the following task: Find the problem –  Hit  the exception Inform that an error has occurred –  Throw  the exception Receives the error infor
Read more

Define a class Student with four data members such as name, roll no.,sub1, and sub2. Define appropriate methods to initialize and display the values of data members. Also calculate total marks and percentage scored by student.

In this program, first we first create a class  Student  which have data members  name, roll_no, sub1, sub2  and one method to read data here  getdata( )  method and show the result here  show( )  method. We have used  java.io.BufferedReader  class to read data from keyboard at runtime. Then we have created an object of Student class in  StudentDemo  class and called the methods of Student class. When you compile the code using  javac StudentDemo.java  command two .class files will be created which are  Student.class  and  StudentDemo.class , this has the advantage that you can reuse your .class file somewhere in other projects without compiling the code again. You can create as many classes as you want but writing many classes in a single file is not recommended as it makes code difficult to read rather you can create single file for every class. You can also group classes in packages for easily managing your code. PROGRAM import java.lang.*; import java.io.*; class Student {
Read more