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how to create custom marker interface in java

Marker/Tagging Interfaces:

An interface with no methods is known as marker or tagged interface.

Why marker interface used:  

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.  Example: Serializable, Clonnable etc. 


public interface Interface_Name {


Let us understand it with a example. We have no. of colleges from which some colleges are of A grade. We have created a AGradeCollegeMarker interface which contains no method and only inform the JVM that it is a A grade college. Every A grade college have to implement AGradeCollegeMarker. In TestCollege class, tester method will print “A grade college.” if object belongs to A grade college.


 * This is marker interface for A grade college.
 * @author CodesJava
public interface AGradeCollegeMarker {

 * This class represents a A grade college.
 * @author CodesJava
public class College1 implements AGradeCollegeMarker{
	//Do something

 * This class represents a, non A grade college.
 * @author CodesJava
public class College2 {
	//Do something

 * This class is used to test the custom marker interface functionality.
 * @author CodesJava
public class TestCollege {
	static void tester(Object obj){
		if (obj instanceof AGradeCollegeMarker) {
                       System.out.println("A grade college.");
	public static void main(String args[]){
		College1 obj1 = new College1();
		College2 obj2 = new College2();
		//test college objects


A grade college.

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