OBSERVER DESIGN PATTERN IN JAVA

/*
OBSERVER DESIGN PATTERN IN JAVA
*/
import java.util.*;
class subject
{

person p1,p2;

subject()
{
p1=new person();
p2=new person();
}
void notify(boolean a)
{
if(a)
{
p2.state=p1.state="changed";

System.out.println(p1);
System.out.println(p2);
}
else
{
System.out.println(p1);
System.out.println(p2);
}

}
public static void main(String[] args)
{
boolean executed=false;
String choice;
subject s=new subject();
Scanner sc=new Scanner(System.in);
while(!executed)
{
System.out.println("SHOULD WE CHANGE STATE ?  Y/N");
choice=sc.nextLine();
if(choice.equals("Y") || choice.equals("y"))
{
s.notify(true);
executed=true;
}
else
s.notify(false);
}
}
}
class person
{//person is the observer;
String state;
person()
{
state="unchanged";
}
public String toString()
{
return state;
}

}

/*
OUTPUT
SHOULD WE CHANGE STATE ?  Y/N
n
unchanged
unchanged
SHOULD WE CHANGE STATE ?  Y/N
n
unchanged
unchanged
SHOULD WE CHANGE STATE ?  Y/N
n
unchanged
unchanged
SHOULD WE CHANGE STATE ?  Y/N
n
unchanged
unchanged
SHOULD WE CHANGE STATE ?  Y/N
y
changed
changed

*/