处理语言：从 ArrayList() 获取内部数组值

发布于 2024-12-09 02:41:44 字数 728 浏览 0 评论 0原文

我正在尝试在处理中使用 ArrayList() 方法。

我有这个：

    ArrayList trackPoints = new ArrayList();

        //inside a loop
        int[] singlePoint = new int[3];

        singlePoint[0] = 5239;
        singlePoint[1] = 42314;
        singlePoint[2] = 1343;
        //inside a loop

    trackPoints.add(singlePoint);

所以基本上我想向我的 ArrayList 添加一个具有三个值的数组“singlePoint”。

这似乎工作正常，因为现在我可以使用 println(trackPoints.get(5)); 并且我得到了这个：

[0] = 5239;
[1] = 42314;
[2] = 1343;

但是我怎样才能获得这个数组的单个值？

println(trackPoints.get(5)[0]); 不起作用。

我收到以下错误： “表达式的类型必须是数组类型，但它解析为对象”

知道我做错了什么吗？如何从这个包含多个数组的 arrayList 中获取单个值？

感谢您的帮助！

原文

I'm trying to use the ArrayList() method in Processing.

I have this:

    ArrayList trackPoints = new ArrayList();

        //inside a loop
        int[] singlePoint = new int[3];

        singlePoint[0] = 5239;
        singlePoint[1] = 42314;
        singlePoint[2] = 1343;
        //inside a loop

    trackPoints.add(singlePoint);

So basically I want to add an array "singlePoint" with three values to my ArrayList.

This seems to work fine, because now I can use println(trackPoints.get(5)); and I get this:

[0] = 5239;
[1] = 42314;
[2] = 1343;

However how can I get a single value of this array?

println(trackPoints.get(5)[0]); doesn't work.

I get the following error:
"The type of the expression must be an array type but it resolved to Object"

Any idea what I'm doing wrong? How can I get single values from this arrayList with multiple arrays in it?

Thank you for your help!

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夜巴黎 2024-12-16 02:41:44

您的 ArrayList 应该输入：

List<int[]> list = new ArrayList<int[]>();

如果不是，那么您使用的是原始列表，它可以包含任何内容。因此，其 get 方法返回 Object （这是所有 Java 对象的根类），并且您必须使用强制转换：

int[] point = (int[]) trackPoints.get(5);
println(point[0]);

您应该阅读有关泛型，并阅读 ArrayList的api文档。

Your ArrayList should by typed :

List<int[]> list = new ArrayList<int[]>();

If it's not, then you're using a raw List, which can contain anything. Its get method thus returns Object (which is the root class of all the Java objects), and you must use a cast:

int[] point = (int[]) trackPoints.get(5);
println(point[0]);

You should read about generics, and read the api doc of ArrayList.

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聽兲甴掵 2024-12-16 02:41:44

ArrayList 类上的 get() 方法返回一个对象，除非您将其与泛型一起使用。所以基本上当你说 trackPoints.get(5) 时，它返回的是一个对象。

它与，

Object obj = list.get(5);

所以你不能调用obj[0]。

为此，您需要先输入大小写，如下所示：

( (int[]) trackPoints.get(5) )[0]

The get() method on ArrayList class returns an Object, unless you use it with generics. So basically when you say trackPoints.get(5), what it returns is an Object.

It's same as,