如何在Java中从另一个类中导入已填充的现成ArrayList？

huangapple
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英文:

How do I import a populated ready-made ArrayList from another class in java?

问题

我正在使用大量导入的数据并在主方法中使用两个类（WeatherStation、WeatherReading）检索其中的某些部分。数据是许多气象站的温度读数（站点ID、名称、纬度、经度、年份、时间、温度等）。我创建了第三个类（SoloSiteIds），其唯一目的是返回一个完整的站点ID的ArrayList，不包含重复项。但是，我无法将ArrayList从其他类导入到我的主方法中。我的SoloSiteIds类如下：

  1. public class SoloSiteIds {
  3.     static ArrayList<Integer> siteIds = new ArrayList<Integer>();
  5.     public SoloSiteIds() {
  6.     }
  8.     public SoloSiteIds(ArrayList<Integer> siteIds) {
  10.         String[] weatherData = WeatherData.getData(); // 获取气象数据
  12.         for (int i = 1; i < weatherData.length; i++) {
  13.             String line = weatherData[i];
  14.             String[] elements = line.split(",");
  16.             String siteid = elements[0];
  17.             int id = Integer.parseInt(siteid);
  18.             if (!siteIds.contains(id)) {
  19.                 siteIds.add(id);
  20.             }
  21.         }
  23.         this.siteIds = siteIds;
  24.     }
  26.     public static ArrayList<Integer> getSiteIds() {
  27.         return siteIds;
  28.     }
  30.     public ArrayList<Integer> setSiteIds(ArrayList<Integer> siteIds) {
  31.         return this.siteIds = siteIds;
  32.     }
  33. }

我尝试导入ArrayList "siteIds" 的主要方法如下：

  1. WeatherStation thisStation = new WeatherStation(id, name, lat, lon);
  2. WeatherReading thisReading = new WeatherReading(year, month, date, hour, windSpeed, temp);
  3. SoloSiteIds siteList = new SoloSiteIds();
  5. String[] weatherData = WeatherData.getData();
  7. for (int i = 1; i < weatherData.length; i++) {
  8.     String line = weatherData[i];
  9.     String[] elements = line.split(",");
  11.     String siteid = elements[0];
  12.     id = Integer.parseInt(siteid);
  13.     thisStation.setId(id);
  14.     thisStation.setName(elements[1]);
  15.     
  16.     String stringLat = elements[2];
  17.     lat = Double.parseDouble(stringLat);
  18.     lat = thisStation.setLat(lat);
  19.     lat = thisStation.setLat(lat);
  21.     String stringLon = elements[3];
  22.     lon = Double.parseDouble(stringLon);
  23.     lat = thisStation.setLon(lon);
  24.     lat = thisStation.setLon(lon);
  26.     String stringTemp = elements[9];
  27.     temp = Double.parseDouble(stringTemp);
  28.     temp = thisReading.setTemp(temp);
  29. }

请注意，上面的代码示例中只有顶部部分与导入ArrayList "siteIds" 有关。您可以尝试使用以下方式来获取ArrayList "siteIds" 的值：

  1. ArrayList<Integer> siteIds = SoloSiteIds.getSiteIds();

这应该能够帮助您在主方法中获取导入的站点ID列表。

英文:

I'm working with a large set of imported data and retrieving certain parts of it in the main method with 2 classes(WeatherStation, WeatherReading).The data is temperature readings at loads of weather stations(station id, name, lat, lon, year, time, temp etc) I made a third class (SoloSiteIds) whose sole purpose was to return a whole and complete ArrayList of the site ids with no duplication. But I cannot import the ArrayList from the other class into my main method. My SoloSiteIds class looks like this:

  1. public class SoloSiteIds {
  3.  static ArrayList &lt;Integer&gt; siteIds = new ArrayList &lt;Integer&gt;();
  4.  
  6.  public SoloSiteIds() {
  7.  }
  8.  
  9.  public SoloSiteIds( ArrayList &lt;Integer&gt; siteIds) {
  10. 	 
  11. 	 String[] weatherData = WeatherData.getData();{ // get the weather data 
  12. 	 
  13. 		 for (int i = 1; i &lt; weatherData.length; i++) {
  14. 				String line = weatherData[i];
  15. 				String[] elements = line.split(&quot;,&quot;); // Split the data at &quot;,
  16. 				
  17. 				String siteid = elements[0]; // convert all the site id&#39;s at index 0 to integers
  18. 				int id = Integer.parseInt(siteid);
  19. 				if(!siteIds.contains(id)) {
  20. 					siteIds.add(id);
  21. 				}
  22. 	 
  23. 	 
  24. 	 this.siteIds=siteIds;
  28. 		 }
  29. 	
  30. }
  31. }
  33. public static ArrayList&lt;Integer&gt; getSiteIds() {
  34. 	return siteIds;
  35. }
  37. public ArrayList&lt;Integer&gt; setSiteIds(ArrayList&lt;Integer&gt; siteIds) {
  38. 	return this.siteIds = siteIds;
  39. }

}

The main method where I am trying to import the ArrayList "siteIds" looks like this:

  1. 		WeatherStation thisStation = new WeatherStation (id, name, lat, lon);
  2. 	WeatherReading thisReading = new WeatherReading(year, month, date, hour, windSpeed, temp);
  3. 	SoloSiteIds siteList= new SoloSiteIds();
  4. 	
  7. 	
  8. 	String[] weatherData = WeatherData.getData();{ // get the weather data
  10. 		
  11. 		for (int i = 1; i &lt; weatherData.length; i++) {
  12. 			String line = weatherData[i];
  13. 			String[] elements = line.split(&quot;,&quot;); // Split the data at &quot;,&quot;	
  14. 			
  15. 	
  16. 			
  17. 				
  19. 					String siteid = elements[0]; // convert all the site id&#39;s at index 0 to integers
  20. 					id = Integer.parseInt(siteid);
  21. 					thisStation.setId(id);
  22. 					
  23. 					thisStation.setName(elements[1]);
  24. 					
  25. 					//parse the different elements into different data types
  26. 					
  27. 					String stringLat = elements[2];    
  28. 					lat= Double.parseDouble(stringLat);
  29. 					lat = thisStation.setLat(lat);
  30. 					lat=thisStation.setLat(lat);
  31. 						
  32. 					String stringLon = elements[3];
  33. 					lon= Double.parseDouble(stringLon);
  34. 					lat = thisStation.setLon(lon);
  35. 					lat=thisStation.setLon(lon);
  36. 					
  37. 					String stringTemp=elements[9];
  38. 					temp=Double.parseDouble(stringTemp);
  39. 					temp=thisReading.setTemp(temp);

Only the top part is relevant. I have tried lots of different variation of .set and .get using "thisList" instance and a new ArrayList like

  1. ArrayList&lt;Integer&gt; siteIds = thisList.setSiteIds();
  2. ArrayList&lt;Integer&gt; siteIds= SoloSiteIds.getSiteIds();
  3. thisList=Siteids.setSiteIds();
  4. thisList=SingleSoloSites.setSiteIds();

etc etc. This might look stupid but im just showing Ive tried numerous things and i am stuck
Thanks

答案1

得分: 1

我认为你的问题是你将siteIds初始化为一个空的ArrayList，但你没有以静态方式设置数据（set方法不是静态的）。

据我所知，根据你的情况，我认为SoloSiteIds类是不必要的。我会使用在你的主类中声明的ArrayList来解决你的问题，并使用在主类中也声明的getSoleIds()方法进行初始化。
getSoleIds()方法应该包含当前在SoleSiteIds初始化程序中的代码。

英文:

I believe your problem is that you are initializing siteIds as an empty Arry list but you are not setting the data in a static way (the set Method is not static).

As far as I am aware of your situation, I belive that the SoloSiteIds class is unnescessary. I would solve your problem with an ArrayList declared in your main class and initialize with a getSoleIds() method also declared in your main class.
The getSoleIds() Method should contain the code currently in the SoleSiteIds initializer.

huangapple
  • 本文由 发表于 2020年8月11日 02:54:48
  • 转载请务必保留本文链接：https://go.coder-hub.com/63346345.html
  • arraylist
  • class
  • getter-setter
  • java
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