ObservedValue.java

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package com.fermod.observer;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

import com.fermod.event.EventPublisher;
import com.fermod.event.ValueChangeListener;

public class ObservedValue<T> extends EventPublisher<ValueChangeListener<T>> implements Serializable {

    private T value;

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

    public void set(T value) {
        set(value, true);
    }

    public void set(T value, boolean notifyChange) {

        T oldValue = this.value;
        this.value = value;

        if(notifyChange && oldValue != value) {
            // Notify the list of registered listeners
            this.notifyListeners(listener -> listener.onValueChanged(oldValue, value)); 
        }

    }

    public T get() {
        return value;
    }

    @Override
    public boolean equals(Object obj) {

        if (obj == null) {
            return false;
        }

        if (!ObservedValue.class.isAssignableFrom(obj.getClass())) {
            return false;
        }

        @SuppressWarnings("unchecked")
        final ObservedValue<T> other = (ObservedValue<T>) obj;
        if ((this.value == null) ? (other.value != null) : !this.value.equals(other.value)) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode() {
        int hash = 17;
        hash = 31 * hash + (this.value != null ? this.value.hashCode() : 0);
        return hash;
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
        out.writeObject(value);
    }

    @SuppressWarnings("unchecked")
    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        this.value = (T) in.readObject();
    }

    private static final long serialVersionUID = 8159940159964193507L;

}