ShapeSubject.java

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package com.example.graphics.observer;
 
import com.example.graphics.model.Shape;
import java.util.ArrayList;
import java.util.List;

public class ShapeSubject {
    private final List<ShapeObserver> observers;
    
    public ShapeSubject() {
        observers = new ArrayList<>();
    }
    
    public void addObserver(ShapeObserver observer) {
        if (!observers.contains(observer)) {
            observers.add(observer);
        }
    }
    
    public void removeObserver(ShapeObserver observer) {
        observers.remove(observer);
    }
    
    public void notifyShapeAdded(Shape shape) {
        for (ShapeObserver observer : observers) {
            observer.onShapeAdded(shape);
        }
    }
    
    public void notifyShapeRemoved(Shape shape) {
        for (ShapeObserver observer : observers) {
            observer.onShapeRemoved(shape);
        }
    }
    
    public void notifyShapeModified(Shape shape) {
        for (ShapeObserver observer : observers) {
            observer.onShapeModified(shape);
        }
    }
}