java - 硬件帮助错误**线程“main”中的异常java.lang.NullPointerException**，程序在命令行中运行良好但不是eclipse或整洁的bean

Question

大家好，我是java新手，需要一个课程帮助，我有一个任务如下。

“设计一个 Java 应用程序，它将读取包含与美国相关的数据的文件。从 1994 年到 2013 年的犯罪统计数据。文件的描述在此文件的末尾。应用程序应提供数据的统计结果，包括：”

长话短说，我创建了在命令行中运行良好的程序，但在 NetBeans/eclipse 中出现以下错误

java.io.FileNotFoundException: Crime.csv (The system cannot find the file specified)
    at java.base/java.io.FileInputStream.open0(Native Method)
    at java.base/java.io.FileInputStream.open(FileInputStream.java:212)
    at java.base/java.io.FileInputStream.<init>(FileInputStream.java:154)
    at java.base/java.io.FileInputStream.<init>(FileInputStream.java:109)
    at java.base/java.io.FileReader.<init>(FileReader.java:60)
    at TestUSCrime.readFile(TestUSCrime.java:22)
    at TestUSCrime.main(TestUSCrime.java:73)

美国犯罪数据类别

`import java.util.ArrayList;
public class USCrimeData`{

    ArrayList<USCrime> crimesList;

    public USCrimeData(ArrayList<USCrime> crimesList) {
        this.crimesList = crimesList;
    }

    private USCrime getCrimeByYear(int year) {
        for (USCrime usCrime : crimesList) {
            if (usCrime.getYear() == year) {
                return usCrime;
            }
        }

        return null;
    }

    public int LowestMurderRateYear() {
        double lowestRate = crimesList.get(0).getMurder();
        int lowestRateYear = crimesList.get(0).getYear();
        double currentRate = 0;

        for (int i = 1; i < crimesList.size(); i++) {
            currentRate = crimesList.get(i).getMurder();
            if (currentRate < lowestRate) {
                lowestRate = currentRate;
                lowestRateYear = crimesList.get(i).getYear();
            }
        }

        return lowestRateYear;
    }

    public int HighestRobberyRateYear() {
        double highestRate = crimesList.get(0).getRobberyRate();
        int highestRateYear = crimesList.get(0).getYear();
        double currentRate = 0;

        for (int i = 1; i < crimesList.size(); i++) {
            currentRate = crimesList.get(i).getRobberyRate();
            if (currentRate > highestRate) {
                highestRate = currentRate;
                highestRateYear = crimesList.get(i).getYear();
            }
        }

        return highestRateYear;
    }

    public int LowestRobberyRateYear() {
        double lowestRate = crimesList.get(0).getRobberyRate();
        int lowestRateYear = crimesList.get(0).getYear();
        double currentRate = 0;

        for (int i = 1; i < crimesList.size(); i++) {
            currentRate = crimesList.get(i).getRobberyRate();
            if (currentRate < lowestRate) {
                lowestRate = currentRate;
                lowestRateYear = crimesList.get(i).getYear();
            }
        }

        return lowestRateYear;
    }

    public int HighestMurderRateYear() {
        double highestRate = crimesList.get(0).getMurder();
        int highestRateYear = crimesList.get(0).getYear();
        double currentRate = 0;

        for (int i = 1; i < crimesList.size(); i++) {
            currentRate = crimesList.get(i).getMurder();
            if (currentRate > highestRate) {
                highestRate = currentRate;
                highestRateYear = crimesList.get(i).getYear();
            }
        }

        return highestRateYear;
    }

    public double MotorVehicleTheftPercentChange() {
        USCrime crimeFrom = getCrimeByYear(1998);
        USCrime crimeTo = getCrimeByYear(2012);

        if (crimeFrom != null && crimeTo != null) {
            long yearFromVehicleTheft = crimeFrom.getMotorVehicleTheft();
            long yearToVehicleTheft = crimeTo.getMotorVehicleTheft();

            double percentChange = ((double) Math.abs(yearToVehicleTheft - yearFromVehicleTheft) / yearFromVehicleTheft)
                    * 100;

            return percentChange;
        }
        return 0;
    }

    public int HighestBurglaryRateYear() {
        double highestRate = crimesList.get(0).getBurglaryRate();
        int highestRateYear = crimesList.get(0).getYear();
        double currentRate = 0;

        for (int i = 1; i < crimesList.size(); i++) {
            currentRate = crimesList.get(i).getBurglaryRate();
            if (currentRate > highestRate) {
                highestRate = currentRate;
                highestRateYear = crimesList.get(i).getYear();
            }
        }

        return highestRateYear;
    }

    public int LowestBurglaryRateYear() {
        double lowestRate = crimesList.get(0).getBurglaryRate();
        int lowestRateYear = crimesList.get(0).getYear();
        double currentRate = 0;

        for (int i = 1; i < crimesList.size(); i++) {
            currentRate = crimesList.get(i).getBurglaryRate();
            if (currentRate < lowestRate) {
                lowestRate = currentRate;
                lowestRateYear = crimesList.get(i).getYear();
            }
        }

        return lowestRateYear;
    }

    public void printPopulationGrowth() {
        System.out.println("\nYear\tGrowth Percentage\n1994\t 0%");
        double growthPercent = 0;
        long currentPopulation;
        long previousPopulation;

        for (int i = 1; i < crimesList.size(); i++) {
            currentPopulation = crimesList.get(i).getPopulation();
            previousPopulation = crimesList.get(i - 1).getPopulation();
            growthPercent = ((double) (currentPopulation - previousPopulation) / previousPopulation) * 100;

            System.out.println(crimesList.get(i).getYear() + "\t" + String.format("%.2f", growthPercent) + " %");
        }
        System.out.println("");
    }
}

***US CRIME CLASS***
`public class USCrime`{

    int year;
    double violentCrimeRate;
    long murder;
    double murderRate;
    double burglaryRate;
    long larcenyTheft;
    long violentCrime;
    long robbery;
    double robberyRate;
    long rape;
    long aggravatedAssault;
    double larcenyTheftRate;
    long motorVehicleTheft;
    long propertyCrime;
    double propertyCrimeRate;
    long burglary;
    double rapeRate;
    long population;
    double aggravatedAssaultRate;
    double motorVehicleTheftRate;

    // constructor
    public USCrime(String[] crimeData) {
        year = Integer.parseInt(crimeData[0]);
        population = Long.parseLong(crimeData[1]);
        violentCrime = Long.parseLong(crimeData[2]);
        violentCrimeRate = Double.parseDouble(crimeData[3]);
        murder = Long.parseLong(crimeData[4]);
        murderRate = Double.parseDouble(crimeData[5]);
        rape = Long.parseLong(crimeData[6]);
        rapeRate = Double.parseDouble(crimeData[7]);
        robbery = Long.parseLong(crimeData[8]);
        robberyRate = Double.parseDouble(crimeData[9]);
        aggravatedAssault = Long.parseLong(crimeData[10]);
        aggravatedAssaultRate = Double.parseDouble(crimeData[11]);
        propertyCrime = Long.parseLong(crimeData[12]);
        propertyCrimeRate = Double.parseDouble(crimeData[13]);
        burglary = Long.parseLong(crimeData[14]);
        burglaryRate = Double.parseDouble(crimeData[15]);
        larcenyTheft = Long.parseLong(crimeData[16]);
        larcenyTheftRate = Double.parseDouble(crimeData[17]);
        motorVehicleTheft = Long.parseLong(crimeData[18]);
        motorVehicleTheftRate = Double.parseDouble(crimeData[19]);
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public double getViolentCrimeRate() {
        return violentCrimeRate;
    }

    public void setViolentCrimeRate(double violentCrimeRate) {
        this.violentCrimeRate = violentCrimeRate;
    }

    public long getMurder() {
        return murder;
    }

    public void setMurder(long murder) {
        this.murder = murder;
    }

    public double getMurderRate() {
        return murderRate;
    }

    public void setMurderRate(double murderRate) {
        this.murderRate = murderRate;
    }

    public double getBurglaryRate() {
        return burglaryRate;
    }

    public void setBurglaryRate(double burglaryRate) {
        this.burglaryRate = burglaryRate;
    }

    public long getLarcenyTheft() {
        return larcenyTheft;
    }

    public void setLarcenyTheft(long larcenyTheft) {
        this.larcenyTheft = larcenyTheft;
    }

    public long getViolentCrime() {
        return violentCrime;
    }

    public void setViolentCrime(long violentCrime) {
        this.violentCrime = violentCrime;
    }

    public long getRobbery() {
        return robbery;
    }

    public void setRobbery(long robbery) {
        this.robbery = robbery;
    }

    public double getRobberyRate() {
        return robberyRate;
    }

    public void setRobberyRate(double robberyRate) {
        this.robberyRate = robberyRate;
    }

    public long getRape() {
        return rape;
    }

    public void setRape(long rape) {
        this.rape = rape;
    }

    public long getAggravatedAssault() {
        return aggravatedAssault;
    }

    public void setAggravatedAssault(long aggravatedAssault) {
        this.aggravatedAssault = aggravatedAssault;
    }

    public double getLarcenyTheftRate() {
        return larcenyTheftRate;
    }

    public void setLarcenyTheftRate(double larcenyTheftRate) {
        this.larcenyTheftRate = larcenyTheftRate;
    }

    public long getMotorVehicleTheft() {
        return motorVehicleTheft;
    }

    public void setMotorVehicleTheft(long motorVehicleTheft) {
        this.motorVehicleTheft = motorVehicleTheft;
    }

    public long getPropertyCrime() {
        return propertyCrime;
    }

    public void setPropertyCrime(long propertyCrime) {
        this.propertyCrime = propertyCrime;
    }

    public double getPropertyCrimeRate() {
        return propertyCrimeRate;
    }

    public void setPropertyCrimeRate(double propertyCrimeRate) {
        this.propertyCrimeRate = propertyCrimeRate;
    }

    public long getBurglary() {
        return burglary;
    }

    public void setBurglary(long burglary) {
        this.burglary = burglary;
    }

    public double getRapeRate() {
        return rapeRate;
    }

    public void setRapeRate(double rapeRate) {
        this.rapeRate = rapeRate;
    }

    public long getPopulation() {
        return population;
    }

    public void setPopulation(long population) {
        this.population = population;
    }

    public double getAggravatedAssaultRate() {
        return aggravatedAssaultRate;
    }

    public void setAggravatedAssaultRate(double aggravatedAssaultRate) {
        this.aggravatedAssaultRate = aggravatedAssaultRate;
    }

    public double getMotorVehicleTheftRate() {
        return motorVehicleTheftRate;
    }

    public void setMotorVehicleTheftRate(double motorVehicleTheftRate) {
        this.motorVehicleTheftRate = motorVehicleTheftRate;
    }

    
}

***TEST CRIME CLASS***
`import java.io.FileReader;
import java.io.BufferedReader;
import java.util.Scanner;
import java.io.IOException;
import java.util.ArrayList;
public class TestUSCrime `
{

    private static long startTime;
    private static long endTime;
    private static Scanner scan;

    private static ArrayList<USCrime> readFile(String fileName) {
        String line = "";
        String[] fileData;
        ArrayList<USCrime> crimeDataList = new ArrayList<>();

        try (BufferedReader br = new BufferedReader(new FileReader(Crime.csv))) {
            line = br.readLine();
            while ((line = br.readLine()) != null) {
                fileData = line.split(",");
                USCrime usCrime = new USCrime(fileData);
                crimeDataList.add(usCrime);
            }

            return crimeDataList;

        } catch (IOException e) {
            System.out.println("Exception occurred.");
            return null;
        }
    }

    private static long getElapsedTime() {
        return (endTime - startTime) / 1000;
    }

    private static void displayMenu() {
        System.out.println("***** Welcome to the US Crime Statistical Application *****\n");
        System.out.println("Enter the number of the question you want answered. Enter 'Q' to quit the program :\n");
        System.out.println("1. What were the percentages in population growth for each consecutive year from 1994 - 2013?");
        System.out.println("2. What year was the Murder rate the highest?");
        System.out.println("3. What year was the Murder rate the lowest?");
        System.out.println("4. What year was the Robbery rate the highest?");
        System.out.println("5. What year was the Robbery rate the lowest?");
        System.out.println("6. What was the total percentage change in Motor Vehicle Theft between 1998 and 2012?");
        System.out.println("7. What year was the Burglary rate the highest?");
        System.out.println("8. What year was the Burglary rate the lowest?");
        System.out.println("Q. Quit the program");
        System.out.print("\nEnter your selection: ");
    }

    /**
     * main method
     */
    String entry = "";
    scan = new Scanner(System.in);

    startTime = System.currentTimeMillis();

    if (args.length == 0) {
        System.out.println("Invalid Argument!");
        return;
    }

    USCrimeData objUSCrimeData = new USCrimeData(readFile(args[0]));

    while (!entry.equalsIgnoreCase("Q")) {
        displayMenu();
        entry = scan.nextLine();

        if (!entry.equalsIgnoreCase("Q")) {

            switch (entry) {
                case "1":
                    objUSCrimeData.printPopulationGrowth();
                    break;
                case "2":
                    System.out.println(
                            "\nThe Murder rate was highest in " + objUSCrimeData.HighestMurderRateYear() + "\n");
                    break;
                case "3":
                    System.out.println(
                            "\nThe Murder rate was lowest in " + objUSCrimeData.LowestMurderRateYear() + "\n");
                    break;
                case "4":
                    System.out.println(
                            "\nThe Robbery rate was highest in " + objUSCrimeData.HighestRobberyRateYear() + "\n");
                    break;
                case "5":
                    System.out.println(
                            "\nThe Robbery rate was lowest in " + objUSCrimeData.LowestRobberyRateYear() + "\n");
                    break;
                case "6":
                    System.out.println("\nThe total percentage change in Motor Vehicle Theft between 1998 and 2012 was "
                            + String.format("%.2f", objUSCrimeData.MotorVehicleTheftPercentChange()) + " %\n");
                    break;
                case "7":
                    System.out.println(
                            "\nThe Burglary rate was highest in " + objUSCrimeData.HighestBurglaryRateYear() + "\n");
                    break;
                case "8":
                    System.out.println("\nThe Burglary Rate was lowest in "
                            + objUSCrimeData.LowestBurglaryRateYear() + "\n");
                    break;
                default:
                    System.out.println("\nInvalid choice. Please Try Again!\n");
                    break;
            }
        } else {
            endTime = System.currentTimeMillis();
            System.out.println("\nThank you for trying the US Crimes Statistics Program.");
            System.out.println("\nElapsed time in seconds was: " + getElapsedTime());
        }
    }

}

标签： java