Create Marker/Tagging Interfaces

An interface with no methods is known as the marker interface. It provides some useful information to JVM/compiler so that JVM/compiler performs some special operations on it. It is used for better readability of code.

Few marker interfaces which are used in java are Random, Serializable, Clonnable etc.

Syntax:

public interface interface_name {

}

Example:

TierACollegeMarker.java

/**

 * This is marker interface for Tier A college.

 * @author rajesh.dixit

 */

public interface TierACollegeMarker {

}

IITD.java

/**

 * This class represents Tier A grade college.

 * @author rajesh.dixit

 */

public class IITD implements TierACollegeMarker {

     //Do something

}

Hindustan.java

/**

 * This class represents a, non-Tier A college.

 * @author rajesh.dixit

 */

public class Hindustan {

     //Do something

}

TestCollege.java

/**

 * This class is used to test the custom marker interface functionality.

 * @author rajesh.dixit

 */

public class TestCollege {

     static void tester(Object obj) {

           if (obj instanceof TierACollegeMarker) {

                System.out.println("Tier A college.");

           }

     }

     public static void main(String args[]) {

           IITD college1 = new IITD();

           Hindustan college2 = new Hindustan();

           /** test college objects.*/

           tester(college1);

           tester(college2);

     }

}