SINGLETON PATTERN IN JAVA

/*
TEJAS J GHALSASI
TEIT
SINGLETON PATTERN IN JAVA
*/
import java.util.*;
public class NoticeBoard {
   
    private static NoticeBoard a;
    String message;
    /**
     * Create private constructor
     */
    private NoticeBoard(){
       
    }
    /**
     * Create a static method to get instance.
     */
    public static NoticeBoard getInstance(){
        if(a == null){
            a = new NoticeBoard();
        }
        return a;
    }
   
    public void getMessage(String msg){
        message=msg;
        System.out.println("message updated \n");
    }
   
    public void postMessage(){
       
        System.out.println("Current message is: "+message);
    }
   
    public static void main(String a[]){
    Scanner sc=new Scanner(System.in);
    NoticeBoard nb = NoticeBoard.getInstance();
        NoticeBoard nb1 = NoticeBoard.getInstance();
        System.out.println("enter message");
        String msg=sc.nextLine();
       
nb.getMessage(msg);
System.out.println("message stored in nb");
nb.postMessage();

System.out.println("message stored in nb1");
nb1.postMessage();
     
      System.out.println("enter a new message ");
       msg=sc.nextLine();
     
nb.getMessage(msg);
System.out.println("message stored in nb");
nb.postMessage();

System.out.println("message stored in nb1");
nb1.postMessage();
    }
}
/*
THIS PROGRAM IS CODED BY TG
*/