Simple Java observer wrapper

SubscribableObserver.java

import java.util.Observable;

public class SubscribableObserver<valueType> extends Observable {

    protected valueType value;

    public SubscribableObserver(valueType value) {
        this.value = value;
    }
    
    public void update(valueType value) {
        this.value = value;
    }
    
    public valueType getValue(valueType value) {
        return value;
    }
    
    interface Subscriber<valueType> {
        void operation(valueType value);
    }

    public void subscribe(Subscriber<valueType> subscriber) {
        this.addObserver((Observable o, Object args) -> {
            subscriber.operation(this.value);
        });
    }
}