Question

我正在编写一个带有csv文件的程序，并将每一行读入一个具有自己字段的USCrimeClass对象数组中。我想通过打印其中一个来查看阵列是否正确，但我得到的是OutOfBounds异常。

import java.io.*;
import java.util.*;
public class USCrimeClass
{
    public int year;
    public int population;
    public int violentCrime;
    public double violentCrimeRate;
    public int manslaughter;
    public double manslaughterRate;
    public int rape;
    public double rapeRate;
    public int robbery;
    public double robberyRate;
    public int assault;
    public double assaultRate;
    public int propertyCrime;
    public double propertyCrimeRate;
    public int burglary;
    public double burglaryRate;
    public int larcenyTheft;
    public double larcenyTheftRate;
    public int vehicleTheft;
    public double vehicleTheftRate;

    public USCrimeClass(String line)
    {
        String[]split=line.split(",");
        year=Integer.parseInt(split[0]);
        population=Integer.parseInt(split[1]);
        violentCrime=Integer.parseInt(split[2]);
        violentCrimeRate=Double.parseDouble(split[3]);
        manslaughter=Integer.parseInt(split[4]);
        manslaughterRate=Double.parseDouble(split[5]);
        rape=Integer.parseInt(split[6]);
        rapeRate=Double.parseDouble(split[7]);
        robbery=Integer.parseInt(split[8]);
        robberyRate=Double.parseDouble(split[9]);
        assault=Integer.parseInt(split[10]);
        assaultRate=Double.parseDouble(split[11]);
        propertyCrime=Integer.parseInt(split[12]);
        propertyCrimeRate=Double.parseDouble(split[13]);
        burglary=Integer.parseInt(split[14]);
        burglaryRate=Double.parseDouble(split[15]);
        larcenyTheft=Integer.parseInt(split[16]);
        larcenyTheftRate=Double.parseDouble(split[17]);
        vehicleTheft=Integer.parseInt(split[18]);
        vehicleTheftRate=Double.parseDouble(split[19]);
    }

    public static void main(String[] args)
    {
        Scanner read = null;
        {
            try
            {
                read=new Scanner(new File("C:\\Crime.csv"));
            }
            catch(FileNotFoundException e)
            {
                System.out.println("The file can't be opened");
                System.exit(0);
            }



            String[] lines = null;

            read.nextLine();
            while(read.hasNextLine())
            {
                lines=read.nextLine().split(",");
            }

            USCrimeClass[] CrimeYear=new USCrimeClass[lines.length];

            for(int i=0;i<lines.length;i++)
            {
                CrimeYear[i]=new USCrimeClass(lines[i]);
            }
            read.close();

            System.out.println(CrimeYear[0]);
        }
    }
}

这是csv文件应该是什么样子

1994,260327173,1130,3.7,3890,39.5,...
1995,250692382,2478,21.5,2230,28.6,...
1996,230492492,4092,22.8,3202,39.4...

这是错误消息

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at USCrimeClass.<init>(USCrimeClass.java:30)
at USCrimeClass.main(USCrimeClass.java:84)

Answer 1

关于此代码：

while(read.hasNextLine())
{
    lines = read.nextLine().split(",");
}

你在这里做的是逐行读取文件，但是你总是用当前读取的行覆盖lines。最后lines将只包含最后一行的拆分内容，而不包含csv文件中的所有行。

将每个读取行添加到列表中，然后这应该有效：

List<String> lines = new ArrayList<>();

read.nextLine();
while(read.hasNextLine())
{
    lines.add(read.nextLine());
}

USCrimeClass[] CrimeYear = new USCrimeClass[lines.size()];

for(int i=0;i<lines.size();i++)
{
    CrimeYear[i]=new USCrimeClass(lines.get(i));
}
read.close();

如果您不想缓冲所有读取行，您还可以直接创建相应的对象：

List<USCrimeClass> crimeClasses = new ArrayList<>();
read.nextLine();
while(read.hasNextLine())
{
    crimeClasses.add(new USCrimeClass(read.nextLine()));
}

read.close();

System.out.println(crimeClasses.get(0));

BTW：我还建议将read.close（）放入finally { ... }块。

将csv文件读入数组后获取OutOfBounds异常

1 个答案: