java: <identifier> 预期与 ArrayList

java: <identifier> expected with ArrayList

提问by A-moc

I have a class named Storage. Storage contains an arraylist of special objects called Products. Each product contains information such as name, price, etc. My code is as follows:

我有一个名为 Storage 的类。存储包含称为产品的特殊对象的数组列表。每个产品都包含名称、价格等信息，我的代码如下：

class Storage{

 Product sprite = new Product("sprite",1.25,30);
 Product pepsi = new Product("pepsi",1.85,45);
 Product orange = new Product("orange",2.25,36);
 Product hershey = new Product("hershey",1.50,33);
 Product brownie = new Product("brownie",2.30,41);
 Product apple = new Product("apple",2.00,15);
 Product crackers = new Product("peanut",3.90,68);
 Product trailmix = new Product("trailmix",1.90,45);
 Product icecream = new Product("icecream",1.65,28);
 Product doughnut = new Product("doughnut",2.75,18);
 Product banana = new Product("banana",1.25,32);
 Product coffee = new Product("coffee",1.30,40);
 Product chips = new Product("chips",1.70,35);

 ArrayList<Product> arl = new ArrayList<Product>();

 //add initial elements to arraylist
 arl.add(sprite);
 arl.add(pepsi);
 arl.add(orange);
 arl.add(hershey);
 arl.add(brownie);
 arl.add(apple);
 arl.add(peanut);
 arl.add(trailmix);
 arl.add(icecream);
 arl.add(doughnut);
 arl.add(banana);
 arl.add(coffee);
 arl.add(chips);
}

Whenever I compile, I get an error message on lines 141-153 stating <identifier> expected. I know it's an elementary problem, but I can't seem to figure this out. Any help is much appreciated.

每当我编译时，我都会在第 141-153 行收到一条错误消息，指出<identifier> expected. 我知道这是一个基本问题，但我似乎无法弄清楚。任何帮助深表感谢。

回答by Cam

You can't call methods like that just in the class body. You have to put methods calls in other methods, or in a constructor.

你不能只在类体中调用这样的方法。您必须将方法调用放入其他方法或构造函数中。

You want this:

你要这个：

class Storage{

    Product sprite = new Product("sprite",1.25,30);
    Product pepsi = new Product("pepsi",1.85,45);
    Product orange = new Product("orange",2.25,36);
    Product hershey = new Product("hershey",1.50,33);
    Product brownie = new Product("brownie",2.30,41);
    Product apple = new Product("apple",2.00,15);
    Product crackers = new Product("peanut",3.90,68);
    Product trailmix = new Product("trailmix",1.90,45);
    Product icecream = new Product("icecream",1.65,28);
    Product doughnut = new Product("doughnut",2.75,18);
    Product banana = new Product("banana",1.25,32);
    Product coffee = new Product("coffee",1.30,40);
    Product chips = new Product("chips",1.70,35);

    ArrayList<Product> arl = new ArrayList<Product>();


    //constructor
    protected Storage(){
        //add initial elements to arraylist
        arl.add(sprite);
        arl.add(pepsi);
        arl.add(orange);
        arl.add(hershey);
        arl.add(brownie);
        arl.add(apple);
        arl.add(peanut);
        arl.add(trailmix);
        arl.add(icecream);
        arl.add(doughnut);
        arl.add(banana);
        arl.add(coffee);
        arl.add(chips);
    }
}

回答by polygenelubricants

The problem is that your initialization code is out of place. You can:

问题是你的初始化代码不合适。你可以：

• Put it in a constructor or other method
• Put it in instance initializer
• Put it as field initializer

• 将其放入构造函数或其他方法中
• 把它放在实例初始化程序中
• 把它作为字段初始值设定项

The last option is the simplest and cleanest solution; it would look something like this:

最后一个选项是最简单、最干净的解决方案；它看起来像这样：

List<Product> arl = new ArrayList<Product>(
  Arrays.asList(
    sprite, pepsi, orange, hershey, brownnie, apple, peanut,
    trailmix, icecream, doughnut, banana, coffee, chips
  )
);

Note also that I switched the type of arlto its interface List<Product>. You should try to work with interfaces rather than concrete implementations whenever possible.

另请注意，我将 的类型切换arl到其 interface List<Product>。您应该尽可能尝试使用接口而不是具体的实现。

回答by James P.

Your class is missing some methods. Use a constructor or a main method (public static void main(String[] args){...}) to fill your ArrayList.

你的班级缺少一些方法。使用构造函数或主方法 (public static void main(String[] args){...}) 来填充您的 ArrayList。