不能将字符串从一个类传递到另一个类

Question

您好，我正在尝试编写一个程序，该程序从逗号分隔的文本文件中获取第三行，然后将其传递给 WeatherDataPoint 类中的 getData 方法，在该方法中，它将字符串拆分为逗号上的单独字符串。然后我希望将字符串变量 date 设置为 dataLine2[7] 的值。然后通过调用驱动程序类的 getDate 方法打印出日期字符串。

public class driver 

{

public static void main(String[] args) 
{
    WeatherDataPoint weather = new WeatherDataPoint();
    String dataLine1 = "";
    String inputFile = "weatherdata.csv";
    Scanner readFile = null;
    try
    {
        readFile = new Scanner (new File(inputFile));
    }
    catch (FileNotFoundException ex)
    {
        System.out.println("Error file not found");
        System.exit(1);
    }

    while (readFile.hasNextLine())
    {

        dataLine1 = readFile.nextLine();

        weather.getData(dataLine1);



    }

    System.out.println(String.format("%s",weather.getDate()));
}

}

public class WeatherDataPoint {
private String date = "";
private String temperature;


public void getData(String dataLine1)
{
    String [] dataLine2 = dataLine1.split(",");
    date = dataLine2[7];
    //long epoc = Long.parseLong(fields[DATE_POS]);
    //Date d = new Date(epoc * 1000);

}


public String getDate()
{
    //return String.format("%s", (date));
    return date;
}

当我运行程序时出现错误

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 7

编辑这里是文本文件中的一行

"1452386100","1","5","29.002591800284698","77.91272888363851","78.21244075516647","86.27","49.8",,"99","0",,"0",,"0","0","49.53002056234984","49.8","49.8",,,,,,,,,,,,,,,,,,,,,"100",,,,,,,,,,,,

我在描述程序时犯了一个错误，我实际上想处理文件中的所有数据，但跳过前三行，抱歉造成混淆。将 dataLine[7] 更改为 dataLine[0] 也可以。

Answer 1

尝试替换这个：

 String [] dataLine2 = dataLine1.split(",");
date = dataLine2[7];

与：

  String [] dataLine2 = dataLine1.split(",");
  date = dataLine2[dataLine2.length-1];

因为在数组 dataLine2 中，您在第 7 个索引中没有元素。

Answer 2

确保您在 csv 文件的第 8 列有日期数据。

Answer 3

您正在尝试从数组dataLine2 的第 8 个单元格中获取值。异常指出此索引超出范围，这意味着数组 dataLine2 没有 8 个单元格。

这意味着您的字符串 dataLine1 在文件的单行中似乎没有 8 个部分。

尝试打印dataLine2 变量的大小，这样您就可以看到一行有多少个字符串部分。然后通过遍历数组中的单元格来获取每个单元格。

编辑：

如果您需要跳过文件的前 3 行，您需要执行以下操作：

WeatherDataPoint weather = new WeatherDataPoint();
String dataLine1 = "";
String inputFile = "weatherdata.csv";
Scanner readFile = null;
try {
    readFile = new Scanner (new File(inputFile));
}
catch (FileNotFoundException ex) {
    System.out.println("Error file not found");
    System.exit(1);
}

    int linesPassed = 0;
    while (readFile.hasNextLine()) {
        String row = readFile.nextLine();
        linesPassed++;
        if (linesPassed > 3) {
            dataLine1 = row;
            weather.getData(dataLine1);
        }
    }
System.out.println(String.format("%s",weather.getDate()));

如果您需要处理整行，最好保存整个 String[] 并根据需要进行处理。这是一个示例代码：

私有 ArrayList 日期 = 新 ArrayList(); 私有字符串温度；

public void getData(String dataLine1){
    String[] rowParts =dataLine1.split(",");
    for(String part : rowParts)
        date.add(part); 
}

public String getDate() {
    //do some processing here, I`ve added a dummy print code
    String allValues = "";
    for(String val : date)
        allValues += val + " ";
    return allValues;
}

对于文件中的示例数据，如下所示：

"1452386100","1","5","29.002591800284698","77.91272888363851","78.21244075516647","86.27","49.8",,"99","0",,"0",,"0","0","49.53002056234984","49.8","49.8",,,,,,,,,,,,,,,,,,,,,"100",,,,,,,,,,,,
"1452386100","1","5","29.002591800284698","77.91272888363851","78.21244075516647","86.27","49.8",,"99","0",,"0",,"0","0","49.53002056234984","49.8","49.8",,,,,,,,,,,,,,,,,,,,,"100",,,,,,,,,,,,
"1452386100","1","5","29.002591800284698","77.91272888363851","78.21244075516647","86.27","49.8",,"99","0",,"0",,"0","0","49.53002056234984","49.8","49.8",,,,,,,,,,,,,,,,,,,,,"100",,,,,,,,,,,,
"0","1","2","3","4","5","6","7",
"0","1","2","3","4","5","6","7",

输出是这样的：

"0" "1" "2" "3" "4" "5" "6" "7" "0" "1" "2" "3" "4" "5" "6" "7" 

根据需要随意扩展和修改。