Just simple and more convenient replacement of java.util.Observable/Observer to implement observer pattern

SimpleObservable.java

package com.example;

import java.util.ArrayList;
import java.util.List;

/**
 * Just simple and more convenient replacement of java.util.Observable/Observer
 * to implement observer pattern
 */
public class SimpleObservable<T> {
    private T value;

    private List<Observer<T>> observers = new ArrayList<>();

    public interface Observer<T> {
        void onChanged(T value);
    }

    public SimpleObservable() {
    }

    public SimpleObservable(T value) {
        this.value = value;
    }

    public void subscribe(Observer<T> observer) {
        if (!observers.contains(observer)) {
            observers.add(observer);
        }
    }

    public void unsubscribe(Observer<T> observer) {
        observers.remove(observer);
    }

    public T get() {
        return value;
    }

    public void set(T value) {
        this.value = value;
        notifyChanged();
    }

    public void notifyChanged() {
        for (Observer<T> observer: observers) {
            observer.onChanged(value);
        }
    }
}