Remove方法,从对象数组中移除对象

所以我有一节课 Pizza :

public class Pizza{

private final int MAX_INGREDIENTS = 5;
private int id;
private String name;
private String description;
private float price;
private PizzaSize size;
private PizzaIngredients[] ingredients;
private int numberOfIngredients;
}

如你所见,我有一个枚举, PizzaSize 这与这个问题无关。

我还有一个 Ingredients 类别:

public class Ingredients {

private int id;
private String name;
private MeasurementUnits measurementUnits;
private int calories;
}

如你所见,我有一个枚举, MeasurementUnits 这也与这个问题无关。

最后,我有一个 PizzaIngredients 类别:

public class PizzaIngredients {

private Ingredients ingredients;
private float quantity;
}

所有这些类都有各自的构造函数方法和所有的setter和getter,为了节省空间和增强清晰度,我选择不将它们放在这里。

所以我写了这个方法,通过id从成分集合中删除成分:

public void removeIngredient(int id) {

if (this.numberOfIngredients > 0) {
    for(int i = 0; i < this.ingredients.length; i++) {
       if (this.ingredients[i] != null && this.ingredients[i].getIngredients().getId() == id) {
          ingredients[i] = null;
       }
    } else {
        System.out.println("Pizza has no ingredients!");
    }
}    

但现在我正在尝试编写不使用and索引的方法 i ,使用 foreach :

    if (this.numberOfIngredients > 0) {
        for (PizzaIngredients ing : this.ingredients) {
            if (ing.getIngredients().getId() == id) {
               ing.setIngredients(null);
            }
        }
    } else {
        System.out.println("Pizza has no ingredients!");
    }

此方法将成分设置为null,但在打印时,

    pizza1.removeIngredient(1);
    System.out.println("Removing ingredient test (pizza1): ");
    for (PizzaIngredients ingredient : collection1) {
        if (ingredient != null) {
            System.out.println("ID: " + ingredient.getIngredients().getId() + "| Name: " + ingredient.getIngredients().getName()
                    + "| Quantity: " + ingredient.getQuantity() + " " + ingredient.getIngredients().getMeasurementUnits());
        }
    }

抛出NullPointerException,同时将该方法与索引一起使用,但它没有。为什么会这样?将第二个方法条件更改为 ing = null 它甚至不起作用,它仍然打印成分。