What is an Interface in Java

What is an Interface in Java

Several methods that relate when grouped together they form interface.These methods have empties bodies commonly know as abstract methods.Classes that implement interface have an obligation of implementing all the interface methods.

How to declare interfaces example.

/**
 *
 * @author Eric
 * Site:www.techoverload.net
 * Date:10/26/2017
 */
public interface Vehicle {
 
    
    public void changeGear(int value);
   
    public void increaseSpeed(int increment);
    
public void decreaseSpeed(int decrement);



}

Implementing Above interface.

To implement Vehicle interface,we will create a class of type of vehicles (Cars).implements keyword  is used in class declaration.

/**
 *
 * @author Eric
 * Site:www.techoverload.net
 * Date:10/26/2017
 */
public class Cars  implements Vehicle{
    
    int gearNumber=1;
    int speed=0;
    
    public void changeGear(int value)
    {
    gearNumber=value;
    }
    public void increaseSpeed(int increment)
    {
    speed=speed+increment;
    }
public void decreaseSpeed(int decrement)
{
speed=speed-decrement;
}
public void outPut()
{
System.out.println("Gear " +gearNumber +":  Speed " +speed);
}

}