如何在静态类中初始化最终静态变量？

发布于 2024-12-18 20:46:14 字数 1012 浏览 1 评论 0原文

所以我使用处理从数据文件中绘制地图。我想存储类中第一行的一些信息。在处理这个类时，它是 PApplet 的内部类，因此它必须是静态类（否则我会得到一个错误：静态字段只能在静态或顶级类型中声明）。

public static class PlacesInfo{
    static final int totalCount;
    static final float xMin;
    static final float yMin;
    static final float xMax;
    static final float yMax;
    static final int populationMax;
    static final int densityMax;


    //Set all static variables once
    static{
      String[] lines =  loadStrings("population.tsv");
      String info = lines[0].substring(2); //to delete some useless char
      String[] infoInit = split(info, ','); //to parse the data of the first line

      totalCount = int(infoInit[0]);
      xMin = float(infoInit[1]);
      xMax = float(infoInit[2]);
      yMin = float(infoInit[3]);
      yMax = float(infoInit[4]);
      populationMax = int(infoInit[6]);
      densityMax = int(infoInit[8]); 
    }
}

当我运行此代码时，出现错误，因为我无法使用 loadStrings() 函数（它是非静态的）。

所以我想要的是拥有可以从“population.tsv”文件初始化的静态最终变量。您有什么想法/建议？

原文

So I'm using Processing to draw a map from a data file. I want to stock some information of the first line inside a class. In processing this class is an inner class of PApplet, so it has to be a static class (Otherwise i get an error: static fieldscan only be declared in static or top level type).

public static class PlacesInfo{
    static final int totalCount;
    static final float xMin;
    static final float yMin;
    static final float xMax;
    static final float yMax;
    static final int populationMax;
    static final int densityMax;


    //Set all static variables once
    static{
      String[] lines =  loadStrings("population.tsv");
      String info = lines[0].substring(2); //to delete some useless char
      String[] infoInit = split(info, ','); //to parse the data of the first line

      totalCount = int(infoInit[0]);
      xMin = float(infoInit[1]);
      xMax = float(infoInit[2]);
      yMin = float(infoInit[3]);
      yMax = float(infoInit[4]);
      populationMax = int(infoInit[6]);
      densityMax = int(infoInit[8]); 
    }
}

When I run this code, I get an error, because I can't use the loadStrings() function (which is non-static).

So what I want is to have static final variables that I can initialize from the "population.tsv" file. What are your ideas/advices?

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送君千里 2024-12-25 20:46:14

1）将方法设为静态，这样就可以了——静态代码必须按顺序必须按顺序编译。将 loadStrings 函数放在静态代码块之前。

请注意：但是 - 您最好简单地创建一个静态的“init”方法，该方法在静态代码块中调用。与您当前的实现不同，这将是可命名和可单元测试的。

2）顺便说一句：你的浮点语法已关闭，必须正确转换。

  int i = (int) 1.4f;

3) 要初始化静态变量，您可以执行以下操作：

声明一个静态 init() 方法，该方法读取文件并初始化静态变量。
在单独的类或静态内部类中创建一个单独的 FileReader 对象，可以调用该对象来读取变量，并从静态代码块中调用它。
（坏主意）将文件读取逻辑放在大静态代码块中。但这会非常难看。

1) Make the method static, and you will be fine -- static code must be in order must be compiled in order. Put the loadStrings function before the static code block.

Please note : However - you might be better off simply creating a single, static , "init" method, which is called in your static code block . This will be nameable and unit-testable, unlike your current implementation.

2) By the way : your float syntax is off, and must to be casted properly.

  int i = (int) 1.4f;

3) To initialize the static variables you can do the following :

Declare a static init() method, which reads the file and initializes the static variables.
Create a separate FileReader object in a separate class, or a static inner class, which can be invoked to read in variables , and invoke it FROM your static code block.
(bad idea) Put the file reading logic inside of your big static code block . this will be very ugly however.

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