Name: ksC84122 Date: 07/26/99


java.util.Observable.addObserver(Observer)
should throw NullPointerException if null parameter is passed.

In JDK 1.3 addObserver(null) returns silently which causes
notifyObservers() throwing an unexpected exception.

Here is the example demonstrating the bug:
--------------------Test.java------------------------
import java.util.*;

class MyObservable extends Observable {
    public void change() {
        super.setChanged();
    }
}

public class Test {
   public static void main(String args[]) {
        MyObservable obj = new MyObservable();
        try {
            obj.addObserver(null);
        } catch(NullPointerException e) {
            System.out.println("NullPointerException in addObserver(null)");
        }

        obj.change();

        try {
            obj.notifyObservers(new Object());
} catch(NullPointerException e) {
            System.out.println("NullPointerException in notifyObservers()");
        }
    }
}

------------- Output under JDK 1.2.2 -------------------------------------
NullPointerException in notifyObservers()


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