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我在一个类中有这个代码，并且希望理想地将adjclose数组列表中的值复制到另一个类以进行进一步处理，同时保留原始数据。

我可以看到在数组被填充 时，arraylist 在println语句之前填充了语句的值。return

然后该main方法遍历 arraylist 以再次显示 arraylist 中每个元素的值adjclose。

我怎样才能adjclose从另一个类访问数组列表以使我能够将它们复制到新的数组列表以进一步处理？

public ArrayList<Double> getadjClose(String symbol) {
    String baseUrl = "http://ichart.finance.yahoo.com/table.csv?ignore=.csv";
    baseUrl += "&s=" + symbol;
    baseUrl += "&a=" + startMonth;
    baseUrl += "&b=" + startDay;
    baseUrl += "&c=" + startYear;
    baseUrl += "&d=" + endMonth;
    baseUrl += "&e=" + endDay;
    baseUrl += "&f=" + endYear;
    baseUrl += "&g=" + freq;
    URL url;
    ArrayList<Double> adjclose = new ArrayList<Double>();
    System.out.print("Opening URL: ");
    System.out.print(baseUrl);
    System.out.println(" ");
    int counter = 0;
    try {
        url = new URL(baseUrl);
        BufferedReader in = new BufferedReader(new InputStreamReader(
                url.openStream()));
        in.readLine(); // Forward Header
        while (true) {
            String thisLine = in.readLine();
            if (thisLine == null) {
                break;
            }
            String[] separatedLine = thisLine.split("[,X]"); // split by commas
            adjclose.add(Double.parseDouble(separatedLine[6]));
            System.out.println(adjclose.get(counter) + " " + counter);
            counter = counter + 1;
        }
        return adjclose;
    } catch (IOException e) {
        return null;
    }
}

我现在对第一个类中的代码进行了更改，如下所示。

package yahooapi;

/**
 *
 * @author RSLOMA
 */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.Calendar;

public class YahooAPI {


int startMonth;
int startDay;
int startYear;

int endMonth;
int endDay;
int endYear;
int TodayDate;

String freq;

public ArrayList<Double> data = new ArrayList<>();


public ArrayList<Double>  getAdjClose(String symbol) throws IOException {
String baseUrl = "http://ichart.finance.yahoo.com/table.csv?ignore=.csv";
baseUrl += "&s=" + symbol;
baseUrl += "&a=" + startMonth;
baseUrl += "&b=" + startDay;
baseUrl += "&c=" + startYear;
baseUrl += "&d=" + endMonth;
baseUrl += "&e=" + endDay;
baseUrl += "&f=" + endYear;
baseUrl += "&g=" + freq;

URL url;

// use a local variable

ArrayList<Double> adjclose = new ArrayList<>(); 

System.out.print("Opening URL: ");
System.out.print(baseUrl);
System.out.println(" ");

int counter = 0;

try {
url = new URL(baseUrl);
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));

in.readLine(); //Forward Header

while (true){
String thisLine = in.readLine();
if (thisLine == null){
break;
}
String[] separatedLine = thisLine.split("[,X]"); // split by commas

adjclose.add(Double.parseDouble(separatedLine[6]));
System.out.println(adjclose.get(counter) + " " + counter);

// update the data once the read is done

data = adjclose;
System.out.println(data.get(counter));

counter = counter + 1;

}


return adjclose;

} catch (IOException e) {
    return null;
}
}


public static void main(String args[]) throws IOException{
YahooAPI y = new YahooAPI();
Calendar cal = Calendar.getInstance();

y.startDay = 1;
y.startMonth = cal.get(Calendar.MONTH) - 1; //0 is jan, so 2 is march
y.startYear = cal.get(Calendar.YEAR) - 3;
System.out.println("Day: " + y.startMonth);
System.out.println("Day: " + y.startDay);
System.out.println("Day: " + y.startYear);

y.endDay = cal.get(Calendar.DATE) - (cal.get(Calendar.DATE) - 1);
y.endMonth = cal.get(Calendar.MONTH); //0 is jan, so 2 is march
y.endYear = cal.get(Calendar.YEAR);

y.freq = "m"; // d for daily frequency, w for weekly, m for monthly

ArrayList<Double> adjclose = y.getAdjClose("^GSPC");

//Iterator<Double> iter = adjclose.iterator();

//System.out.println("Returned Adjusted Close Values:");
//while (iter.hasNext()){
//System.out.println(iter.next());


int ArrayLngth = adjclose.size();

System.out.print("Array length = " + ArrayLngth + "    ");
}

    public ArrayList<Double> getAdjClose() {

        for (int counter = 0; counter<data.size(); counter++) {

            System.out.println(data.get(counter) + " " + counter);

    }



        return (ArrayList<Double>) data.clone();


    }



}

我在另一个包中有另一个类，我想用于计算，将原始数据元素保留在原始数组中，并将新计算的数据保存在第二类的数组中。另一个类的开始代码如下。如何调用以获取在 data.clone() 中克隆的数据？

package PortfolioDesign;

/**
 *
 * @author RSLOMA
 */


public class MonthlyReturns {


        }
4

3 回答 3

1

在你的第一个类中有一个方法，它将创建数组的克隆并返回克隆，然后从你的第二个类调用该方法。

于 2012-05-24T14:37:07.480 回答
1

如果多次使用结果，我会将方法拆分为

  • 一种数据收集方法
  • 一种数据检索方法

然后数据收集器填充该类的一个成员：

private ArrayList<Double> data = new ArrayList<Double>();

public void  fillAdjClose(String symbol) throws IOException {
    String baseUrl = "http://ichart.finance.yahoo.com/table.csv?ignore=.csv";
    baseUrl += "&s=" + symbol;
    baseUrl += "&a=" + startMonth;
    baseUrl += "&b=" + startDay;
    baseUrl += "&c=" + startYear;
    baseUrl += "&d=" + endMonth;
    baseUrl += "&e=" + endDay;
    baseUrl += "&f=" + endYear;
    baseUrl += "&g=" + freq;
    URL url;

    // use a local variable
    ArrayList<Double> adjclose = new ArrayList<Double>();
    System.out.print("Opening URL: ");
    System.out.print(baseUrl);
    System.out.println(" ");
    int counter = 0;
    url = new URL(baseUrl);
    BufferedReader in = new BufferedReader(new InputStreamReader(
            url.openStream()));
    in.readLine(); // Forward Header
    while (true) {
        String thisLine = in.readLine();
        if (thisLine == null) {
            break;
        }
        String[] separatedLine = thisLine.split("[,X]"); // split by commas
        adjclose.add(Double.parseDouble(separatedLine[6]));
        System.out.println(adjclose.get(counter) + " " + counter);
        counter = counter + 1;
    }

    // update the date once the read is done
    data = adjclose;
}

public ArrayList<Double> getAdjClose() {
    return (ArrayList<Double>) data.clone();
}

您可以随时调用 getAdjClose() 并始终获取上次读取数据的副本。

除非您还需要元素的副本，否则您始终可以将 clone() 用于 ArrayList。由于您使用的是不可变的 Double，因此无需复制元素。

于 2012-05-24T14:58:22.350 回答
0

如果你想发布adjclosesay from Class Ato的值，Class B那么包含类ClassA应该有一个可以称为 my 的 getter 方法ClassB。

要保留原始数据，您应该发布一份副本，adjClose而不是原始列表本身。另外需要注意的是，你应该做一个深层克隆而不是浅层克隆。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public classA {
   private List<Double> adjclose = null;

   public List<Double> getAdjClose(){
     List<Double> returnValue = new ArrayList<Double>();
     if(adjclose != null) {
        returnValue.addAll(adjclose); // this will ensure that if caller makes any changes to adjClose, copy of classA remains intact.
        return returnValue;
     }
     return Collections.emptyList();
   }    
}

然后调用者类 ClassB 将创建 ClassA 的实例并在其上调用 getAdjClose()。

import java.util.List;
public class ClassB {
   public static void main(String[] args){
      ClassA classA = new ClassA();
      List<Double> list = classA.getAdjClose();
      System.out.println(list);
      list.set(0, new Double(11));
      System.out.println(list);
      System.out.println(classA.getAdjClose());
   }
}
于 2012-05-24T14:38:31.403 回答